研究者データベース

力石 嘉人(チカライシ ヨシト)
低温科学研究所 共同研究推進部
教授

基本情報

所属

  • 低温科学研究所 共同研究推進部

職名

  • 教授

学位

  • 博士(理学)(東京都立大学)

ホームページURL

J-Global ID

研究キーワード

  • 有機地球化学   同位体生態学   同位体生理学   生物地球化学   

研究分野

  • 自然科学一般 / 宇宙惑星科学 / 有機地球化学

研究活動情報

論文

  • Ryuji Toue, Kazuhiko Fujita, Masashi Tsuchiya, Yoshito Chikaraishi, Yoko Sasaki, Naohiko Ohkouchi
    Progress in Earth and Planetary Science 9 1 2022年12月 
    Abstract Based on laboratory observations, planktonic foraminifers are omnivorous, feeding zooplankton and phytoplankton. Spinose species tend toward greater dependence on zooplankton prey than on phytoplankton prey, while non-spinose species are more adapted to herbivorous diets. However, the trophic activity of planktonic foraminifers in the natural environment and their trophic positions in the marine food web have not yet been fully understood. The trophic position (TP) of two non-spinose species, Neogloboquadrina dutertrei and Pulleniatina obliquiloculata, was determined by differences in the nitrogen isotopic composition between two amino acids (glutamic acid and phenylalanine). Results show that TP values of N. dutertrei were ~ 2.4, indicating dependence on omnivorous (mixed herbivorous and carnivorous) diets, while those of P. obliquiloculata were ~ 2.1, indicating dependence on herbivorous diets. Together with previous laboratory observations, these TP values suggest that N. dutertrei is a detritivore or scavenger, while P. obliquiloculata is generally a herbivore. This trophic niche separation likely allows these two planktonic foraminiferal species to live within a similar depth zone in the open water column and provides a clue for understanding causes of spatial and temporal changes in their relative abundances in living and sediment assemblages.
  • Naoto F. Ishikawa, Nanako O. Ogawa, Yuchen Sun, Yoshito Chikaraishi, Yoshinori Takano, Naohiko Ohkouchi
    Limnology and Oceanography: Methods 2022年07月19日 [査読有り]
  • Yoshihiro Fujiwara, Masaru Kawato, Jan Yde Poulsen, Hitoshi Ida, Yoshito Chikaraishi, Naohiko Ohkouchi, Kazumasa Oguri, Shinpei Gotoh, Genki Ozawa, Sho Tanaka, Masaki Miya, Tetsuya Sado, Katsunori Kimoto, Takashi Toyofuku, Shinji Tsuchida
    Scientific Reports 11 1 2021年12月 
    AbstractA novel species of the family Alepocephalidae (slickheads), Narcetes shonanmaruae, is described based on four specimens collected at depths greater than 2171 m in Suruga Bay, Japan. Compared to other alepocephalids, this species is colossal (reaching ca. 140 cm in total length and 25 kg in body weight) and possesses a unique combination of morphological characters comprising anal fin entirely behind the dorsal fin, multiserial teeth on jaws, more scale rows than congeners, precaudal vertebrae less than 30, seven branchiostegal rays, two epurals, and head smaller than those of relatives. Mitogenomic analyses also support the novelty of this large deep-sea slickhead. Although most slickheads are benthopelagic or mesopelagic feeders of gelatinous zooplankton, behavioural observations and dietary analyses indicate that the new species is piscivorous. In addition, a stable nitrogen isotope analysis of specific amino acids showed that N. shonanmaruae occupies one of the highest trophic positions reported from marine environments to date. Video footage recorded using a baited camera deployed at a depth of 2572 m in Suruga Bay revealed the active swimming behaviour of this slickhead. The scavenging ability and broad gape of N. shonanmaruae might be correlated with its colossal body size and relatively high trophic position.
  • Naoto F. Ishikawa, Nanako O. Ogawa, Yoshito Chikaraishi, Moto-omi Yamaguchi, Katsunori Fujikura, Yosuke Miyairi, Yusuke Yokoyama, Toshi Nagata, Naohiko Ohkouchi
    Frontiers in Marine Science 8 2021年05月05日 
    To study the influence of different ocean currents on the trophic spectra found in a sympatric fish community, we analyzed the radiocarbon contents (Δ14C) and stable carbon (δ13C) and nitrogen (δ15N) isotopic compositions in their bulk muscle tissues and the δ15N of individual amino acids in 26 species of demersal fish collected from off Tohoku (Pacific coast), northeastern Japan. The Δ14C values of the fish varied from –42 to +41‰, consistent with the Δ14C of the dissolved inorganic carbon in the cold Oyashio Current (typically about –50‰) and the warm Kuroshio Current (typically about +50‰). The trophic positions (TPs) of the fish estimated from the δ15N values of amino acids increased from 3.1 to 4.5 with increasing snout length. A negative correlation was observed between Δ14C and TP in gadiform fish and flatfish, suggesting that the Oyashio Current delivers a high TP diet to these fish groups. These results suggest that the trophic ecology of marine fish in the coastal western North Pacific is primarily controlled by the two major surface water currents, but is also significantly influenced by a combination of species-specific feeding and migration strategies.
  • Yuko Takizawa, Yoshinori Takano, Bohyung Choi, Prarthana S. Dharampal, Shawn A. Steffan, Nanako O. Ogawa, Naohiko Ohkouchi, Yoshito Chikaraishi
    Progress in Earth and Planetary Science 7 1 2020年12月 
    Abstract Stable nitrogen (15N/14N) and carbon (13C/12C) isotopic compositions of amino acids in organisms have widely been employed as a powerful tool to evaluate resource utilization and trophic connection among organisms in diverse ecosystems. However, little is known about the physiological factors or mechanisms responsible for determining the isotopic discrimination (particularly for carbon) within amino acids of organisms. In the present study, we investigated the inter-trophic discrimination of nitrogen and carbon isotopes within amino acids (Δδ15NAA and Δδ13CAA, respectively) using four consumer–diet pairs. Each pairing illustrates a metabolic perspective of isotopic fractionation of amino acids. The Δδ15NAA values in these combinations reveal a trend consistent with those observed in many other combinations in previous studies. This further validates a standard scenario: the deamination preferentially removes 14N amino group from diet-derived amino acids, leaving behind the 15N-enriched amino acids in consumer biomass. The Δδ15NAA values thus mirror the activity of amino acid deamination in consumers. In contrast, the trends in the Δδ13CAA value suggest a different metabolic fate for the amino acid carbon isotope. Based on our results, we predict the following scenario: decarboxylation preferentially removes 12C α-carbon (i.e., carbonyl-carbon) from pyruvic acid in glycolysis, and from α-ketoglutaric acid in the tricarboxylic acid cycle, leaving behind the 13C-enriched both pyruvic and α-ketoglutaric acids. The 13C is then transferred to amino acids that are synthesized from the 13C-enriched precursor molecules within consumers. The Δδ13CAA values therefore mirror the pathways of de novo amino acid synthesis in consumers. The proposed link between nitrogen and carbon isotopes can refine our knowledge of the potential processes affecting the isotopic fractionation within diet and consumer compartments, as well as environmental samples. Graphical abstract
  • D Xing, B Choi, Y Takizawa, R Fan, S Sugaya, M Tuchiya, N Ohkouchi, Y Chikaraishi
    Marine Ecology Progress Series 2020年
  • Extraterrestrial ribose and other sugars in primitive meteorites.
    Furukawa Y, Chikaraishi Y, Ohkouchi N, Ogawa N, Glavin D. P, Dworkin J. P, Abe C, Nakamura T
    PNAS 116 24440 - 24445 2019年11月 [査読有り][通常論文]
  • Takeuchi Riko, Chikaraishi Yoshito, Ogawa Nanako O, Furota Satoshi, Ohkouchi Naohiko, Aoki Motohide, Uchida Tatsuya, Umemura Tomonari, Kumata Hidetoshi
    BUNSEKI KAGAKU 68 5 297 - 306 2019年05月 [査読有り][通常論文]
  • Yu Itahashi, Yilmaz Selim Erdal, Halil Tekin, Lubna Omar, Yutaka Miyake, Yoshito Chikaraishi, Naohiko Ohkouchi, Minoru Yoneda
    American Journal of Physical Anthropology 168 4 676 - 686 2019年04月 [査読有り][通常論文]
     
    © 2019 Wiley Periodicals, Inc. Objective: The inhabitants of several sites in the Upper Tigris Valley, such as Hakemi Use, domesticated animals and cereals during the Pottery Neolithic period, while the inhabitants in this valley were hunter–gatherers in the Pre-Pottery Neolithic period, consuming freshwater and terrestrial food resources. However, there is considerable uncertainty surrounding whether or not changes in dietary food composition accompanied the shift in food production away from foraging. In order to reveal the impact of the development of agriculture on the human diet over the Pre-Pottery and Pottery Neolithic periods in this region, we analyzed the isotopic compositions of amino acids from the farmers at the Hakemi Use Pottery Neolithic site, and compared them with those from the Pre-Pottery hunter–gatherers in the close region. Materials and Methods: Herein, we report the nitrogen isotopic compositions of amino acids, as well as both carbon and nitrogen isotopic compositions of bulk collagen, from human and faunal remains collected from Hakemi Use. Results: Whereas freshwater resources were consumed by hunter–gatherers in this region during the Pre-Pottery period, the δ 15 N values of glutamic acid (δ 15 N Glu ) and phenylalanine (δ 15 N Phe ) suggest that freshwater food resources were rarely consumed by inhabitants following the development of agriculture. Discussion: Despite living in similar settings by the Tigris as its inhabitants during the Pre-Pottery period, the farmers of the Pottery Neolithic period depended less on freshwater resources for their diets relative to the hunter–gatherers of the Pre-Pottery Neolithic period.
  • Morra Kaycee E, Chikaraishi Yoshito, Gandhi Hasand, James Helen F, Rossman Sam, Wiley Anne E, Raine Andre F, Beck Jessie, Ostrom Peggy H
    OECOLOGIA 189 2 395 - 406 2019年02月 [査読有り][通常論文]
  • Alex S. J. Wyatt, Rui Matsumoto, Yoshito Chikaraishi, Yosuke Miyairi, Yusuke Yokoyama, Keiichi Sato, Nao Ohkouchi, Toshi Nagata
    ECOLOGICAL MONOGRAPHS 89 1 2019年02月 [査読有り][通常論文]
     
    Intra-species variability in foraging strategies may be common, which has significant implications for efforts to understand and manage enigmatic species like the whale shark Rhincodon typus. The ecological relevance of differences in tissue isotopes within and between individuals in the context of foraging however depends on understanding tissue turnover times and carbon (Delta C-13) and nitrogen (Delta N-15) discrimination, which can vary with physiology, metabolism, and diet quality. Here, we examine isotope dynamics in captive R. typus as a basis for enhanced ecological insights into wild populations of the world's largest fish and other enigmatic species. A variable diet, principally consisting of two krill (Euphausia pacifica and Euphausia superba) provided an average of 48 +/- 20 MJ/d (mean +/- SD), or 2.7 +/- 1.3 times basal metabolic requirements. On this diet, in agreement with allometric relationships, large body sizes (3,000-4,000 kg) were matched by slow plasma and cartilage turnover rates (empirically derived as 9 months and 3 yr, respectively), which provide tissue-specific limits on the timescales over which we can isotopically detect diet changes in this species. Average diet-to-tissue discrimination showed significant variation between tissues (plasma and cartilage), and among growing and fasting individuals (Delta C-13 range, 1.5 to 5.5 parts per thousand; Delta N-15 range, -0.1 to 2.9 parts per thousand). Assimilation rates increased with temperature and were higher for the smaller E. pacifica (15 +/- 2 mm) than E. superba (48 +/- 2 mm). Growth significantly lowered both Delta N-15(plasma) and Delta N-15(cartilage), with inappetence markedly reducing Delta N-15(plasma) and Delta C-13(plasma), as well as significantly altering blood biochemistry. Captive findings facilitated the first robust multi-tissue growth- and nutrition-corrected isotope analysis of a wild R. typus population, suggesting individual foraging specialization on low trophic level mid-ocean or coastal prey. Long-term fasting during ocean-basin-scale migrations may be common and such metabolic effects should be carefully quantified when isotopically assessing intra-species foraging differences. The metabolically constrained multi-tissue, multi-isotope approach described can facilitate ecological insights that are indispensable for effective conservation and management of globally threatened, but poorly understood, species by identifying differences in key foraging areas and target prey within and between individuals.
  • Itahashi, Yu, Erdal, Yilmaz Selim, Tekin, Halil, Omar, Lubna, Miyake, Yutaka, Chikaraishi, Yoshito, Ohkouchi, Naohiko, Yoneda, Minoru
    American journal of physical anthropology 168 4 676 - 686 WILEY 2019年01月 [査読有り][通常論文]
     
    [OBJECTIVE] The inhabitants of several sites in the Upper Tigris Valley, such as Hakemi Use, domesticated animals and cereals during the Pottery Neolithic period, while the inhabitants in this valley were hunter-gatherers in the Pre-Pottery Neolithic period, consuming freshwater and terrestrial food resources. However, there is considerable uncertainty surrounding whether or not changes in dietary food composition accompanied the shift in food production away from foraging. In order to reveal the impact of the development of agriculture on the human diet over the Pre-Pottery and Pottery Neolithic periods in this region, we analyzed the isotopic compositions of amino acids from the farmers at the Hakemi Use Pottery Neolithic site, and compared them with those from the Pre-Pottery hunter-gatherers in the close region. [MATERIALS AND METHODS] Herein, we report the nitrogen isotopic compositions of amino acids, as well as both carbon and nitrogen isotopic compositions of bulk collagen, from human and faunal remains collected from Hakemi Use. [RESULTS] Whereas freshwater resources were consumed by hunter-gatherers in this region during the Pre-Pottery period, the δ N values of glutamic
  • Haruna Sugahara, Yoshinori Takano, Shogo Tachibana, Iyo Sugawara, Yoshito Chikaraishi, Nanako O. Ogawa, Naohiko Ohkouchi, Akira Kouchi, Hisayoshi Yurimoto
    Geochemical Journal 53 1 5 - 20 2019年 [査読有り][通常論文]
     
    © 2019 by The Geochemical Society of Japan. Interstellar ice is a reaction site for molecular evolution. Gaseous molecules are frozen at low temperature (~10 K) to form ice mantles and the energy supplied by UV photons and other energy sources can lead to the synthesis of complex organics. Nitrogen-containing organic molecules are of special interest because of their biomolecular importance and their anomalous stable nitrogen isotopic composition ( 15 N/ 14 N) in the interstellar dust environment. Thus, N-containing organic molecules are the keys to understanding the evolution of organic molecules and the solar system. We focused on amino acids and amines in refractory organic residues formed from ultraviolet (UV) irradiated interstellar ice analogues. We developed analytical techniques that enable the identification of the small quantities of molecules formed from the simulated interstellar ice analogues. Organic residue analysis of the UV-irradiated H 2 O-CH 3 OH-NH 3 ice showed the formation of three amines (methylamine, ethylamine and propylamine) and 11 amino acids (e.g., glycine, a-alanine, balanine, sarcosine, a-aminobutyric acid and b-aminoisobutyric acid). Furthermore, the compound-specific isotope analysis of nitrogen within the amino acids and the bulk organic film revealed that little isotopic fractionation occurred during formation in the simulated environment.
  • Takuro NUNOURA, Yoshito CHIKARAISHI, Haruyuki ATOMI
    KAGAKU TO SEIBUTSU 57 1 7 - 9 2018年12月20日
  • Chang Ni-Na, Lin Li-Hung, Tu Tzu-Hsuan, Jeng Ming-Shiou, Chikaraishi Yoshito, Wang Pei-Ling
    PLOS ONE 13 10 2018年10月17日 [査読有り][通常論文]
  • Takano Yoshinori, Chikaraishi Yoshito, Imachi Hiroyuki, Miyairi Yosuke, Ogawa Nanako O, Kaneko Masanori, Yokoyama Yusuke, Krueger Martin, Ohkouchi Naohiko
    SCIENTIFIC REPORTS 8 2018年09月24日 [査読有り][通常論文]
  • Ishikawa Naoto F, Chikaraishi Yoshito, Takano Yoshinori, Sasaki Yoko, Takizawa Yuko, Tsuchiya Masashi, Tayasu Ichiro, Nagata Toshi, Ohkouchi Naohiko
    LIMNOLOGY AND OCEANOGRAPHY-METHODS 16 9 607 - 620 2018年09月 [査読有り][通常論文]
  • Tsuchiya Masashi, Chikaraishi Yoshito, Nomaki Hidetaka, Sasaki Yoko, Tame Akihiro, Uematsu Katsuyuki, Ohkouchi Naohiko
    ECOLOGY AND EVOLUTION 8 16 8380 - 8395 2018年08月 [査読有り][通常論文]
  • Compound-specific isotope analysis of benthic foraminifer amino acids suggests microhabitat variability in rocky-shore environments
    Tsuchiya M, Chikaraishi Y, Nomaki H, Sasaki Y, Tame A, Uematsu K, Ohkouchi N
    Ecology and Evolution 00 1 - 16 2018年07月 [査読有り][通常論文]
  • Yuichi I. Naito, Yoshito Chikaraishi, Dorothée G. Drucker, Naohiko Ohkouchi, Patrick Semal, Christoph Wißing, Hervé Bocherens
    Journal of Human Evolution 117 56 - 60 2018年04月01日 [査読有り][通常論文]
  • Takuro Nunoura, Yoshito Chikaraishi, Rikihisa Izaki, Takashi Suwa, Takaaki Sato, Takeshi Harada, Koji Mori, Yumiko Kato, Masayuki Miyazaki, Shigeru Shimamura, Katsunori Yanagawa, Aya Shuto, Naohiko Ohkouchi, Nobuyuki Fujita, Yoshihiro Takaki, Haruyuki Atomi, Ken Takai
    Science (New York, N.Y.) 359 6375 559 - 563 2018年02月02日 [査読有り][通常論文]
     
    Inorganic carbon fixation is essential to sustain life on Earth, and the reductive tricarboxylic acid (rTCA) cycle is one of the most ancient carbon fixation metabolisms. A combination of genomic, enzymatic, and metabolomic analyses of a deeply branching chemolithotrophic Thermosulfidibacter takaii ABI70S6T revealed a previously unknown reversible TCA cycle whose direction was controlled by the available carbon source(s). Under a chemolithoautotrophic condition, a rTCA cycle occurred with the reverse reaction of citrate synthase (CS) and not with the adenosine 5'-triphosphate-dependent citrate cleavage reactions that had been regarded as essential for the conventional rTCA cycle. Phylometabolic evaluation suggests that the TCA cycle with reversible CS may represent an ancestral mode of the rTCA cycle and raises the possibility of a facultatively chemolithomixotrophic origin of life.
  • Yu Itahashi, Akira Tsuneki, Sean P. Dougherty, Yoshito Chikaraishi, Naohiko Ohkouchi, Minoru Yoneda
    Journal of Archaeological Science: Reports 17 775 - 784 2018年02月 [査読有り][通常論文]
     
    © 2017 Elsevier Ltd We report here stable nitrogen isotope values of amino acids and stable carbon and nitrogen isotope values of collagen in human (n = 18) and faunal remains from Tell el-Kerkh, which was a large settlement in the northern Levant during the Neolithic period. A unique outdoor communal cemetery involving > 240 individual burials was found in the Pottery Neolithic levels at Tell el-Kerkh. To test the hypothesis that the burial locations of individuals within the cemetery were determined by household units sharing food resources, we separated individuals from one layer into seven groups within the cemetery, and compared the isotope values of collagen, glutamic acid, and phenylalanine. The results of analysis of individual skeletons in the cemetery suggest that the early farmers had different isotope values based on their burial locations, perhaps indicating distinct household burial spaces.
  • Chelsey Blanke, Yoshito Chikaraishi, M. Jake Vander Zanden
    Ecosphere 9 1 2018年01月01日 [査読有り][通常論文]
     
    Over the last 100 yr, anthropogenic stressors have decimated the assemblage of deepwater coregonines that once underpinned the food webs of the Laurentian Great Lakes. As a part of ongoing restoration efforts, fisheries managers are interested in reintroducing deepwater coregonines from remnant populations to reestablish historical food web connections. However, little is known about historical trophic position and niche partitioning among deepwater coregonines in the Great Lakes. We used nitrogen stable isotope analysis of amino acids to compare trophic position of museum-preserved (1920s) and present-day forage fishes in Lakes Michigan and Superior. In the 1920s, deepwater coregonines exhibited clear trophic niche partitioning, with trophic positions spanning a full trophic level. Additionally, species trophic positions were tightly conserved between lakes. In Lake Superior, trophic niche partitioning has been maintained over the last 100 yr, but trophic position has shifted downward by ∼0.5 trophic level. The more dramatic species loss in Lake Michigan corresponds with a sharp reduction in trophic niche breadth over time. Our study reveals remarkable trophic niche breadth among deepwater coregonines prior to the major anthropogenic impacts on the Laurentian Great Lakes and provides a food web benchmark for restoring the historical trophic diversity of this iconic species flock. Key words: compound-specific Coregonus species food webs Lake Michigan Lake Superior museum specimens niche partitioning species reintroduction stable isotopes trophic compression.
  • Akiko S. Goto, Kasumi Miura, Takashi Korenaga, Takashi Hasegawa, Naohiko Ohkouchi, Yoshito Chikaraishi
    Geochemical Journal 52 3 273 - 280 2018年 [査読有り][通常論文]
     
    Isotopic fractionation of nitrogen associated with the trophic transfer of amino acids in food webs has recently been used as a powerful tool to estimate the accurate trophic levels of heterotrophic organisms. During the grazing process (i.e., trophic transfer), the amino acid, glutamic acid, is significantly enriched in 15N (by ∼6-9%) from diets to consumer heterotrophs this is most likely caused by isotopic fractionation with the preferential deamination of 14N-amino group in glutamic acid during its metabolism. However, few studies determined the isotopic fractionation factor (α) of this process, which limits our understanding of the mechanism responsible for the isotopic fractionation and thus restricts its applicability in assessing the mass and energy transfers with respect to the amino acid assimilation/dissimilation cycle in the biosphere. In this study, we evaluate the α value associated with the enzymatic deamination of glutamic acid in vitro. Glutamic acid is gradually enriched in 15N by up to 4.0%, when the deamination flux is increased up to 45.4%. The α value calculated is 0.9938 ± 0.0005 if the Rayleigh fractionation model is applied to the enrichment in 15N. Thus, we demonstrate the relationship between isotopic fractionation and deamination flux: for example, 8.0% fractionation corresponds to that 72 ± 3% of the diet-derived glutamic acid is deaminated in the consumer species at each shift of trophic levels in a food web.
  • Ogawa Nanako O, Ohkouchi Naohiko, Nomaki Hidetaka, Chikaraishi Yoshito, Fujikura Katsunori, Kitazato Hiroshi
    NIPPON SUISAN GAKKAISHI 84 5 897 - 900 2018年 [査読有り][通常論文]
  • Urai Atsushi, Takahashi Koji, Chikaraishi Yoshito, Fukushima Kazuo
    GEOCHEMICAL JOURNAL 52 6 E15 - E20 2018年 [査読有り][通常論文]
  • Urai Atsushi, Takahashi Koji, Chikaraishi Yoshito, Fukushima Kazuo
    GEOCHEMICAL JOURNAL 52 4 E15 - E20 2018年 [査読有り][通常論文]
  • Takizawa Yuko, Chikaraishi Yoshito
    Researches in Organic Geochemistry 33 1 1 - 6 2017年12月 [査読有り][通常論文]
  • Kiyotaka Takishita, Yoshito Chikaraishi, Goro Tanifuji, Naohiko Ohkouchi, Tetsuo Hashimoto, Katsunori Fujikura, Andrew J. Roger
    JOURNAL OF EUKARYOTIC MICROBIOLOGY 64 6 897 - 900 2017年11月 [査読有り][通常論文]
     
    It is widely held that sterols are key cyclic triterpenoid lipids in eukaryotic cell membranes and are synthesized through oxygen-dependent multienzyme pathways. However, there are known exceptions-ciliated protozoans, such as Tetrahymena, along with diverse low-oxygen-adapted eukaryotes produce, instead of sterols, the cyclic triterpenoid lipid tetrahymanol that does not require molecular oxygen for its biosynthesis. Here, we report that a number of anaerobic microbial eukaryotes (protists) utilize neither sterols nor tetrahymanol in their membranes. The lack of detectable sterol-like compounds in their membranes may provide an opportunity to reconsider the physiological function of sterols and sterol-like lipids in eukaryotes.
  • Naohiko Ohkouchi, Yoshito Chikaraishi, Hilary G. Close, Brian Fry, Thomas Larsen, Daniel J. Madigan, Matthew D. McCarthy, Kelton W. McMahon, Toshi Nagata, Yuichi I. Naito, Nanako O. Ogawa, Brian N. Popp, Shawn Steffan, Yoshinori Takano, Ichiro Tayasu, Alex S. J. Wyatt, Yasuhiko T. Yamaguchi, Yusuke Yokoyama
    ORGANIC GEOCHEMISTRY 113 150 - 174 2017年11月 [査読有り][通常論文]
     
    Compound-specific isotopic analysis of amino acids (CSIA-AA) has emerged in the last decade as a powerful approach for tracing the origins and fate of nitrogen in ecological and biogeochemical studies. This approach is based on the empirical observation that source amino acids (SAAs) (i.e., phenylalanine), fractionate N-15 very little (< 0.5 parts per thousand) during trophic transfer, whereas trophic AAs (TAAs) (i.e., glutamic acid), are greatly (similar to 6-8 parts per thousand) enriched in N-15 during each trophic step. The differential fractionation of these two AA groups can provide a valuable estimate of consumer trophic position that is internally indexed to the baseline delta N-15 value of the integrated food web. In this paper, we critically review the analytical methods for determining the nitrogen isotopic composition of AAs by gas chromatography-isotope-ratio mass spectrometry. We also discuss methodological considerations for accurate trophic position assessment of organisms using CSIA-AA. We then discuss the advantages and challenges of the CSIA-AA approach using published case studies across a range of topics, including trophic position assessment in various ecosystems, reconstruction of ancient human diets, reconstruction of animal migration and environmental variability, and assessment of marine organic matter dynamics with new classification of microbial fractionation patterns. It is clear that the CSIA-AA approach can provide unique insight into the sources, cycling, and trophic modification of organic nitrogen as it flows through systems. However, this approach will be greatly improved through continued exploration into how biochemical, physiological, and ecological mechanisms affect isotopic fractionation of individual AAs. We end this review with a perspective on future work that will promote the evolution of the rapidly growing field of CSIA-AA. (C) 2017 Elsevier Ltd. All rights reserved.
  • Caitlin J. Campbell, David M. Nelson, Nanako O. Ogawa, Yoshito Chikaraishi, Naohiko Ohkouchi
    SCIENTIFIC REPORTS 7 2017年11月 [査読有り][通常論文]
     
    Bats perform important ecosystem services, but it remains difficult to quantify their dietary strategies and trophic position (TP) in situ. We conducted measurements of nitrogen isotopes of individual amino acids (delta N-15(AA)) and bulk-tissue carbon (delta C-13(bulk)) and nitrogen (delta N-15(bulk)) isotopes for nine bat species from different feeding guilds (nectarivory, frugivory, sanguivory, piscivory, carnivory, and insectivory). Our objective was to assess the precision of delta N-15(AA)-based estimates of TP relative to other approaches. TPs calculated from delta N-15 values of glutamic acid and phenylalanine, which range from 8.3-33.1% and 0.7-15.4% respectively, varied between 1.8 and 3.8 for individuals of each species and were generally within the ranges of those anticipated based on qualitative dietary information. The delta N-15(AA) approach reveals variation in TP within and among species that is not apparent from delta C-15(bulk) data, and delta N-15(AA) data suggest that two insectivorous species (Lasiurus noctivagans and Lasiurus cinereus) are more omnivorous than previously thought. These results indicate that bats exhibit a trophic discrimination factor (TDF) similar to other terrestrial organisms and that delta N-15(AA) provides a reliable approach for addressing questions about variation in the TP of bats that have heretofore proven elusive.
  • Yasuhiko T. Yamaguchi, Yoshito Chikaraishi, Yoshinori Takano, Nanako O. Ogawa, Hiroyuki Imachi, Yusuke Yokoyama, Naohiko Ohkouchi
    ORGANIC GEOCHEMISTRY 111 101 - 112 2017年09月 [査読有り][通常論文]
     
    The nitrogen isotopic composition of amino acids (delta N-15(AA)) is a promising tool for estimating the trophic position and nitrogen sources of organisms in grazing food webs. The utility of delta N-15(AA) analysis of microbial processes in the biogeochemistry remains uncertain, because information about the delta N-15(AA) values of chemotrophic microbes are still limited. In this study, we report the delta N-15(AA) values in five cultured heterotrophic or chemolithoautotrophic microbes (one fungus, one bacterium, and three archaea) with controlled nitrogen sources in synthetic media. When the microbes were grown on ammonium, the apparent nitrogen isotopic fractionation of amino acids relative to glutamic acid in the microbes (e.g., -3.0 +/- 1.0 parts per thousand for phenylalanine) was similar to those in algae. When the microbes were grown on a free amino acid mixture, the delta N-15 offsets of amino acids in the microbial cells relative to the amino acids in the culture media (e.g., + 8.2 +/- 0.8 parts per thousand for glutamic acid and +0.1 +/- 0.2 parts per thousand for phenylalanine) were close to the standard isotopic fractionation between animals and their diets. These results suggest that the delta(15)N(AA)d pattern can be used to distinguish two end-member metabolic modes in microbes (i.e., de novo synthesis of amino acids from inorganic nitrogen vs. assimilation of amino acids from environments). We also discussed the effects of metabolic pathways on the delta N-15(AA) values and their fractionation with respect to the diversity of amino acid metabolism in microbes. These findings will form an important baseline for interpreting the delta N-15(AA) values of organisms and detritus in natural environments. (C) 2017 Elsevier Ltd. All rights reserved.
  • Chelsey M. Blanke, Yoshito Chikaraishi, Yuko Takizawa, Shawn A. Steffan, Prarthana S. Dharampal, M. Jake Vander Zanden
    CANADIAN JOURNAL OF FISHERIES AND AQUATIC SCIENCES 74 8 1291 - 1297 2017年08月 [査読有り][通常論文]
     
    Compound-specific nitrogen stable isotope analysis provides an approach for estimating animal trophic position that may overcome key issues associated with stable isotope analysis of bulk tissue. Yet compound-specific trophic discrimination factors have not been estimated for a broad range of habitats, taxa, and diets. We conducted a controlled-feeding experiment to characterize the variation in compound-specific (TDFAA) and bulk (TDFBulk) trophic discrimination factors of four freshwater fish species fed on three distinct diets. We also compared TDFAA of fish muscle and scale to evaluate the viability of scales for making food web inferences. Mean +/- 1 SDTDFBulk was 2.2% +/- 0.9%, and there were significant effects of species and diet trophic position on TDFBulk. Mean +/- 1 SD TDFAA was 6.9% +/- 0.8%. Although there was no effect of species on TDFAA, there were significant differences in TDFAA across the three diets. TDFAA from fish scales were not significantly different from those of muscle. Our study illustrates the advantages of estimating trophic position using compound-specific stable isotopes and the need for continued investigation of factors resulting in variation in TDF values.
  • Bohyung Choi, Sun-Yong Ha, Jae Seong Lee, Yoshito Chikaraishi, Naohiko Ohkouchi, Kyung-Hoon Shin
    Limnology and Oceanography 62 4 1426 - 1435 2017年07月01日 [査読有り][通常論文]
     
    Numerous studies have used stable isotope analysis (SIA) of carbon and nitrogen within the bulk tissues of organisms to determine the trophic structure among organisms in a food web. Recently, SIA has evolved to compound-specific stable isotope analysis (CSIA) of nitrogen within amino acids to significantly reduce the uncertainty in the estimated trophic position (TP) of organisms based on the isotopic difference between glutamic acid and phenylalanine within a single organism. However, because the initial offset (β) between glutamic acid and phenylalanine differs between aquatic algae (ca. +3.4‰) and vascular plants (ca. −8.4‰) in food webs that rely on both resources, β should be replaced by a value adapted to the admixture of primary producers for each specimen. In this study, we established a new method involving the β value (βmix) of each consumer specimen determined based on its bulk tissue δ13C value and successfully obtained realistic TPs (TPmix) for organisms in a complex seagrass meadow food web. Remarkable differences between the TPmix and traditional TPalgal values were found in deposit feeders due to the large contribution of seagrass to their basal resources. The estimated TPs of organisms increased by up to 1.5 units (from TPalgal to TPmix), in terms of trophic transfer, when their diets included substantial seagrass-derived contributions. Thus, combinatorial analysis of the amino acid δ15N and specimen-specific βmix values provides better understanding of the trophic interactions in food webs, even in complex seagrass meadow ecosystems.
  • Bohyung Choi, Sun-Yong Ha, Jae Seong Lee, Yoshito Chikaraishi, Naohiko Ohkouchi, Kyung-Hoon Shin
    LIMNOLOGY AND OCEANOGRAPHY 62 4 1426 - 1435 2017年07月 [査読有り][通常論文]
     
    Numerous studies have used stable isotope analysis (SIA) of carbon and nitrogen within the bulk tissues of organisms to determine the trophic structure among organisms in a food web. Recently, SIA has evolved to compound-specific stable isotope analysis (CSIA) of nitrogen within amino acids to significantly reduce the uncertainty in the estimated trophic position (TP) of organisms based on the isotopic difference between glutamic acid and phenylalanine within a single organism. However, because the initial offset (beta) between glutamic acid and phenylalanine differs between aquatic algae (ca. +3.4 parts per thousand) and vascular plants (ca. -8.4 parts per thousand) in food webs that rely on both resources, beta should be replaced by a value adapted to the admixture of primary producers for each specimen. In this study, we established a new method involving the beta value (beta(mix)) of each consumer specimen determined based on its bulk tissue delta C-13 value and successfully obtained realistic TPs (TPmix) for organisms in a complex seagrass meadow food web. Remarkable differences between the TPmix and traditional TPalgal values were found in deposit feeders due to the large contribution of seagrass to their basal resources. The estimated TPs of organisms increased by up to 1.5 units (from TPalgal to TPmix), in terms of trophic transfer, when their diets included substantial seagrass-derived contributions. Thus, combinatorial analysis of the amino acid delta N-15 and specimen-specific beta(mix) values provides better understanding of the trophic interactions in food webs, even in complex seagrass meadow ecosystems.
  • Dorothee G. Drucker, Yuichi I. Naito, Stephane Pean, Sandrine Prat, Laurent Crepin, Yoshito Chikaraishi, Naohiko Ohkouchi, Simon Puaud, Martina Laznickova-Galetova, Marylene Patou-Mathis, Aleksandr Yanevich, Herve Bocherens
    SCIENTIFIC REPORTS 7 2017年07月 [査読有り][通常論文]
     
    Relatively high N-15 abundances in bone collagen of early anatomically modern humans in Europe have often been interpreted as a specific consumption of freshwater resources, even if mammoth is an alternative high N-15 prey. At Buran-Kaya III, access to associated fauna in a secured archaeological context and application of recently developed isotopic analyses of individuals amino acids offer the opportunity to further examine this hypothesis. The site of Buran-Kaya III is located in south Crimea and has provided a rich archaeological sequence including two Upper Palaeolithic layers, from which human fossils were retrieved and directly dated as from 37.8 to 33.1 ka cal BP. Results from bulk collagen of three human remains suggests the consumption of a high N-15 prey besides the contribution of saiga, red deer, horse and hare, whose butchered remains were present at the site. In contrast to bulk collagen, phenylalanine and glutamic acid N-15 abundances reflect not only animal but also plant protein contributions to omnivorous diet, and allow disentangling aquatic from terrestrial resource consumption. The inferred human trophic position values point to terrestrial-based diet, meaning a significant contribution of mammoth meat, in addition to a clear intake of plant protein.
  • Yu Itahashi, Yutaka Miyake, Osamu Maeda, Osamu Rondo, Hitomi Hongo, Wim Van Neer, Yoshito Chikaraishi, Naohiko Ohkouchi, Minoru Yoneda
    JOURNAL OF ARCHAEOLOGICAL SCIENCE 82 40 - 49 2017年06月 [査読有り][通常論文]
     
    We report here the stable nitrogen isotope composition(delta N-15) of individual amino acids and the delta N-15 and delta C-13 content of collagen from human and faunal remains collected from Hasankeyf Hoyfik, an early Neolithic site in the upper Tigris valley. Based on the delta N-15 of collagen only, the contributions of freshwater resources to the diet of the hunter-gatherers were difficult to clearly identify relative to terrestrial resources. However, analysis of the nitrogen isotope composition of individual amino acids enabled the identification of minor contributions from freshwater resources to the diet in a community primarily dependent on terrestrial resources. Individual variability suggested that some individuals at Hasankeyf Hoyfik used freshwater resources, whereas others probably depended primarily on terrestrial food resources. The importance of freshwater resources as food for this hunter-gatherer community was variable among groups and depended on burial location and time of burial. (C) 2017 Elsevier Ltd. All rights reserved.
  • Takishita, Kiyotaka, Chikaraishi, Yoshito, Tanifuji, Goro, Ohkouchi, Naohiko, Hashimoto, Tetsuo, Fujikura, Katsunori, Roger, Andrew J
    The Journal of eukaryotic microbiology 64 6 897 - 900 WILEY 2017年05月 [査読有り][通常論文]
     
    It is widely held that sterols are key cyclic triterpenoid lipids in eukaryotic cell membranes and are synthesized through oxygen-dependent multi-enzyme pathways. However, there are known exceptions-ciliated protozoans, such as Tetrahymena, along with diverse low-oxygen adapted eukaryotes produce, instead of sterols, the cyclic triterpenoid lipid tetrahymanol that does not require molecular oxygen for its biosynthesis. Here, we report that a number of anaerobic microbial eukaryotes (protists) utilize neither sterols nor tetrahymanol in their membranes. The lack of detectable sterol-like compounds in their membranes may provide an opportunity to reconsider the physiological function of sterols and sterol-like lipids in eukaryotes. This article is protected by copyright. All rights reserved.
  • Yuko Takizawa, Prarthana S. Dharampal, Shawn A. Steffan, Yoshinori Takano, Naohiko Ohkouchi, Yoshito Chikaraishi
    ECOLOGY AND EVOLUTION 7 9 2916 - 2924 2017年05月 [査読有り][通常論文]
     
    The differential discrimination of nitrogen isotopes (N-15/N-14) within amino acids in consumers and their diets has been routinely used to estimate organismal tropic position (TP). Analogous isotopic discrimination can occur within plants, particularly in organs lacking chloroplasts. Such discrimination likely arises from the catabolic deamination of amino acids, resulting in a numerical elevation of estimated TP, within newly synthesized biomass. To investigate this phenomenon, we examined the 15N/14N of amino acids (delta N-15(AA)) in spring leaves and flowers from eight deciduous and two annual plants. These plants were classified on the basis of their time of bloom, plants that bloomed when their leaves were absent (Type I) versus plants that bloomed while leaves were already present (Type II). Based on the delta N-15(AA) values from leaves, both plant types occupied comparable and ecologically realistic mean TPs (= 1.0 +/- 0.1, mean +/- 1 sigma). However, the estimated TPs of flowers varied significantly Type I: 2.2 +/- 0.2; Type II: 1.0 +/- 0.1). We hypothesize that these results can be interpreted by the following sequence of events: (1) Type I floral biomass is synthesized in absence of active photosynthesis; (2) the catabolic deamination of amino acids in particular, leaves behind N-15 in the residual pool of amino acids; and (3) the incorporation of these N-15-enriched amino acids within the biomass of Type I flowers results in the numerical elevation of the TPs. In contrast, the actively photosynthesizing Type II leaves energetically sustain the synthesis of Type II flower biomass, precluding any reliance on catabolic deamination of amino acids. Amino acids within Type II flowers are therefore isotopically comparable to the Type II leaves. These findings demonstrate the idiosyncratic nature of the delta N-15(AA) values within autotrophic organs and have implications for interpreting trophic hierarchies using primary producers and their consumers.
  • Kiyotaka Takishita, Yoshihiro Takaki, Yoshito Chikaraishi, Tetsuro Ikuta, Genki Ozawa, Takao Yoshida, Naohiko Ohkouchi, Katsunori Fujikura
    GENOME BIOLOGY AND EVOLUTION 9 5 1148 - 1160 2017年05月 [査読有り][通常論文]
     
    Sterols are key cyclic triterpenoid lipid components of eukaryotic cellular membranes, which are synthesized through complex multienzyme pathways. Similar to most animals, Bathymodiolus mussels, which inhabit deep-sea chemosynthetic ecosystems and harbor methanotrophic and/or thiotrophic bacterial endosymbionts, possess cholesterol as their main sterol. Based on the stable carbon isotope analyses, it has been suggested that host Bathymodiolus mussels synthesize cholesterol using a sterol intermediate derived from the methanotrophic endosymbionts. To test this hypothesis, we sequenced the genome of the methanotrophic endosymbiont in Bathymodiolus platifrons. The genome sequence data demonstrated that the endosymbiont potentially generates up to 4,4-dimethyl-cholesta-8,14,24-trienol, a sterol intermediate in cholesterol biosynthesis, from methane. In addition, transcripts for a subset of the enzymes of the biosynthetic pathway to cholesterol downstream from a sterol intermediate derived from methanotroph endosymbionts were detected in our transcriptome data for B. platifrons. These findings suggest that this mussel can de novo synthesize cholesterol from methane in cooperation with the symbionts. By in situ hybridization analyses, we showed that genes associated with cholesterol biosynthesis from both host and endosymbionts were expressed exclusively in the gill epithelial bacteriocytes containing endosymbionts. Thus, cholesterol production is probably localized within these specialized cells of the gill. Considering that the host mussel cannot de novo synthesize cholesterol and depends largely on endosymbionts for nutrition, the capacity of endosymbionts to synthesize sterols may be important in establishing symbiont-host relationships in these chemosynthetic mussels.
  • Shawn A. Steffan, Yoshito Chikaraishi, Prarthana S. Dharampal, Jonathan N. Pauli, Christelle Guedot, Naohiko Ohkouchi
    ECOLOGY AND EVOLUTION 7 10 3532 - 3541 2017年05月 [査読有り][通常論文]
     
    Detritivory is the dominant trophic paradigm in most terrestrial, aquatic, and marine ecosystems, yet accurate measurement of consumer trophic position within detrital (="brown") food webs has remained unresolved. Measurement of detritivore trophic position is complicated by the fact that detritus is suffused with microbes, creating a detrital complex of living and nonliving biomass. Given that microbes and metazoans are trophic analogues of each other, animals feeding on detrital complexes are ingesting other detritivores (microbes), which should elevate metazoan trophic position and should be rampant within brown food webs. We tested these hypotheses using isotopic (15N) analyses of amino acids extracted from wild and laboratory-cultured consumers. Vertebrate (fish) and invertebrate detritivores (beetles and moths) were reared on detritus, with and without microbial colonization. In the field, detritivorous animal specimens were collected and analyzed to compare trophic identities among laboratory-reared and free-roaming detritivores. When colonized by bacteria or fungi, the trophic positions of detrital complexes increased significantly over time. The magnitude of trophic inflation was mediated by the extent of microbial consumption of detrital substrates. When detrital complexes were fed to vertebrate and invertebrate animals, the consumers registered similar degrees of trophic inflation, albeit one trophic level higher than their diets. The wild-collected detritivore fauna in our study exhibited significantly elevated trophic positions. Our findings suggest that the trophic positions of detrital complexes rise predictably as microbes convert nonliving organic matter into living microbial biomass. Animals consuming such detrital complexes exhibit similar trophic inflation, directly attributable to the assimilation of microbe-derived amino acids. Our data demonstrate that detritivorous microbes elevate metazoan trophic position, suggesting that detritivory among animals is, functionally, omnivory. By quantifying the impacts of microbivory on the trophic positions of detritivorous animals and then tracking how these effects propagate "up" food chains, we reveal the degree to which microbes influence consumer groups within trophic hierarchies. The trophic inflation observed among our field-collected fauna further suggests that microbial proteins represent an immense contribution to metazoan biomass. Collectively, these findings provide an empirical basis to interpret detritivore trophic identity, and further illuminate the magnitude of microbial contributions to food webs.
  • Naoto F. Ishikawa, Yoshito Chikaraishi, Naohiko Ohkouchi, Aya R. Murakami, Ichiro Tayasu, Hiroyuki Togashi, Jun-ichi Okano, Yoichiro Sakai, Tomoya Iwata, Michio Kondoh, Noboru Okuda
    SCIENTIFIC REPORTS 7 2017年05月 [査読有り][通常論文]
     
    The relationship between biodiversity and ecosystem functioning is an important theme in environmental sciences. We propose a new index for configuration of the biomass pyramid in an ecosystem, named integrated trophic position (iTP). The iTP is defined as a sum of trophic positions (i.e. the average number of steps involved in biomass transfer) of all the animals in a food web integrated by their individual biomass. The observed iTP for stream macroinvertebrates ranged from 2.39 to 2.79 and was negatively correlated with the species density and the Shannon-Wiener diversity index of the local community. The results indicate a lower efficiency of biomass transfer in more diverse communities, which may be explained by the variance in edibility hypothesis and/or the trophic omnivory hypothesis. We found a negative effect of biodiversity on ecosystem functioning.
  • Branwen Williams, Benoit Thibodeau, Yoshito Chikaraishi, Naohiko Ohkouchi, Andrew Walnum, Andréa G. Grottoli, Patrick L. Colin
    Limnology and Oceanography 62 2 399 - 407 2017年03月01日 [査読有り][通常論文]
     
    The depth of the thermocline and associated nitricline in the western Pacific warm pool (WPWP) vary over time in response to changes in larger ocean-atmosphere climate patterns. A shoaling of the nitricline in the WPWP brings nitrate-rich seawater (NO-3 > 4 μmol kg−1) above the base of the euphotic zone, stimulating primary productivity. Here, we test if decadal variability in the nitricline depth is driving changes in regional primary productivity and source nitrate dynamics. We use the nitrogen isotopic composition (δ15N) of amino acids in the skeleton of a proteinaceous coral collected from the base of the euphotic zone in the WPWP. In proteinaceous corals, as in most organic life, the δ15N of phenylalanine matches that of the ambient nitrate while the δ15N of trophic amino acids reflect subsequent trophic transfer of the nitrogen prior to incorporation into the coral's food, suspended particulate organic matter. Consistency of the trophic position of the coral calculated from the δ15N composition of the coral skeletal amino acids over its 56 yr lifespan suggest that decadal variability in nitricline depth and subsequent shifts in nitrate availability to the euphotic zone have not impacted primary productivity offshore of Palau in the WPWP. This is important when considering the current external forcing of Pacific Ocean climate patterns and the resulting impacts on the global carbon cycle in the Palau region of the WPWP.
  • Naoto F. Ishikawa, Fumio Hayashi, Yoko Sasaki, Yoshito Chikaraishi, Naohiko Ohkouchi
    ECOLOGY AND EVOLUTION 7 6 1674 - 1679 2017年03月 [査読有り][通常論文]
     
    The trophic discrimination factor (TDF) of nitrogen isotopes (N-15/N-14) within amino acids, between a stream-dwelling dobsonfly larva (Protohermes grandis: Megaloptera; Corydalidae) and its diet (chironomid larvae), was determined in controlled feeding experiments. Last-instar larvae of P.grandis were collected from the Yozawa-gawa River, central Japan, and reared in the laboratory. After fed to satiation for 1month, one group of larvae was each fed one living chironomid larva per day for 4weeks, while a second group was starved for 8weeks. The larvae were harvested at intervals and the nitrogen isotopic composition of glutamic acid (N-15(Glu)) and phenylalanine (N-15(Phe)) were determined to calculate TDF. The mean TDF of satiated and starved larvae were 7.1 parts per thousand +/- 0.5 parts per thousand (n=3) and 7.3 parts per thousand +/- 0.5 parts per thousand (n=5), respectively. Thus, the TDF for P.grandis larvae in this study was similar to that reported for other arthropods (approximately 7 parts per thousand) and was independent of satiation or starvation. A previous study of wild P.grandis larvae, based on the N-15(Glu) and N-15(Phe) values, estimated its trophic position (TP) as approximately 2.0 +/- 0.1 (n=5), a low value close to that of algivores, although they are generally characterized as carnivores (usually accepted as TP3). The TDF for P.grandis larvae suggests that their low TPs in nature were caused by incorporation of vascular plant-derived amino acids (with a different N-15 profile from that of algae) and not by an unusually low TDF or by the effects of the satiation/starvation on amino acid metabolism.
  • Branwen Williams, Benoit Thibodeau, Yoshito Chikaraishi, Naohiko Ohkouchi, Andrew Walnum, Andrea G. Grottoli, Patrick L. Colin
    LIMNOLOGY AND OCEANOGRAPHY 62 2 399 - 407 2017年03月 [査読有り][通常論文]
     
    The depth of the thermocline and associated nitricline in the western Pacific warm pool (WPWP) vary over time in response to changes in larger ocean-atmosphere climate patterns. A shoaling of the nitricline in the WPWP brings nitrate-rich seawater (NO3- > 4 mu mol kg(-1)) above the base of the euphotic zone, stimulating primary productivity. Here, we test if decadal variability in the nitricline depth is driving changes in regional primary productivity and source nitrate dynamics. We use the nitrogen isotopic composition (delta N-15) of amino acids in the skeleton of a proteinaceous coral collected from the base of the euphotic zone in the WPWP. In proteinaceous corals, as in most organic life, the delta N-15 of phenylalanine matches that of the ambient nitrate while the delta N-15 of trophic amino acids reflect subsequent trophic transfer of the nitrogen prior to incorporation into the coral's food, suspended particulate organic matter. Consistency of the trophic position of the coral calculated from the delta N-15 composition of the coral skeletal amino acids over its 56 yr lifespan suggest that decadal variability in nitricline depth and subsequent shifts in nitrate availability to the euphotic zone have not impacted primary productivity offshore of Palau in the WPWP. This is important when considering the current external forcing of Pacific Ocean climate patterns and the resulting impacts on the global carbon cycle in the Palau region of the WPWP.
  • Peggy H. Ostrom, Anne E. Wiley, Helen F. James, Sam Rossman, William A. Walker, Elise F. Zipkin, Yoshito Chikaraishi
    PROCEEDINGS OF THE ROYAL SOCIETY B-BIOLOGICAL SCIENCES 284 1851 2017年03月 [査読有り][通常論文]
     
    Human-induced ecological change in the open oceans appears to be accelerating. Fisheries, climate change and elevated nutrient inputs are variously blamed, at least in part, for altering oceanic ecosystems. Yet it is challenging to assess the extent of anthropogenic change in the open oceans, where historical records of ecological conditions are sparse, and the geographical scale is immense. We developed millennial-scale amino acid nitrogen isotope records preserved in ancient animal remains to understand changes in food web structure and nutrient regimes in the oceanic realmof theNorth PacificOcean (NPO). Ourmillennial-scale isotope records of amino acids in bone collagen in a wideranging oceanic seabird, the Hawaiian petrel (Pterodroma sandwichensis), showed that trophic level declined over time. The amino acid records do not support a broad-scale increase in nitrogen fixation in the North Pacific subtropical gyre, rejecting an earlier interpretation based on bulk and amino acid specific d15N chronologies for Hawaiian deep-sea corals and bulk d15N chronologies for the Hawaiian petrel. Rather, our work suggests that the food web structure in the NPO has shifted at a broad geographical scale, a phenomenon potentially related to industrial fishing.
  • Haruna Sugahara, Yoshinori Takano, Nanako O. Ogawa, Yoshito Chikaraishi, Naohiko Ohkouchi
    ACS EARTH AND SPACE CHEMISTRY 1 1 24 - 29 2017年03月 [査読有り][通常論文]
     
    Adsorption is a fundamental phenomenon that occurs at various interfaces; however, the isotopic fractionation in stable isotopes associated with this process has not yet been well documented for most molecules. In this study, we conducted ammonia adsorption experiments on two silicate minerals, montmorillonite and saponite, to determine the nitrogen isotopic fractionation during the process. Ammonia adsorbed on these minerals is up to +44(parts per thousand) enriched in N-15 relative to initial ammonia. The degree of N-15 enrichment has a negative correlation with the adsorption ratio of ammonia. These enrichments are remarkably large compared to those reported in other physicochemical (e.g., evaporation) or biological (e.g., enzymatic reaction) processes. On the basis of these results, we can predict that preferential accumulation of (NH3)-N-15 occurs by adsorption on mineral surfaces, which may explain the heterogeneity of the N-15/N-14 ratio in the solar system.
  • Ohkouchi Naohiko, Shibata H, Chikaraishi Y, Nomaki H, Ogawa N. O, Nagata T, Goto T, Fujikura K, Kitazato H
    JOURNAL OF OCEANOGRAPHY 72 4 629 - 639 Oceanographic Society of Japan 2016年08月 [査読有り][通常論文]
  • Yuichi I. Naito, Mietje Germonpre, Yoshito Chikaraishi, Naohiko Ohkouchi, Dorothee G. Drucker, Keith A. Hobson, Mark A. Edwards, Christoph Wissing, Herve Bocherens
    JOURNAL OF QUATERNARY SCIENCE 31 6 598 - 606 2016年08月 [査読有り][通常論文]
     
    Insights into causes of extinction in fossil animals can contribute to an understanding of how environmental or anthropogenic processes may affect extant animals. Cave bears that went extinct in the late Pleistocene in Europe have been considered largely herbivorous based on tooth, skull and jaw morphology. Nitrogen and carbon isotopic composition (N-15, C-13) of bone collagen of many cave bears having values similar to or lower than those of coeval herbivores support an exclusive plant diet and their occurrence in habitats with denser vegetation. A complicating aspect of this hypothesis is that isotopic compositions of bulk collagen, especially those of nitrogen, could reflect environmental fluctuation as well as behavioural and physiological traits, which are not related to trophic position and so may lead to uncertainty in palaeodietary reconstruction. Here we show that N-15 analysis of individual collagen amino acids of fossil bears from Goyet Cave (Belgium) indicates that cave bears had a constant trophic position of 1.9-2.1, indicating purely herbivorous diets, while brown bears had a trophic position of 2.0-2.4, indicating a slightly more omnivorous diet. Results might support the hypothesis of the extinction of cave bear due to the inflexibility in feeding habits.
  • Yuichi I. Naito, Yoshito Chikaraishi, Dorothee G. Drucker, Naohiko Ohkouchi, Patrick Semal, Christoph Wissing, Herve Bocherens
    JOURNAL OF HUMAN EVOLUTION 93 82 - 90 2016年04月 [査読有り][通常論文]
     
    d This study provides a refined view on the diet and ecological niche of Neanderthals. The traditional view is that Neanderthals obtained most of their dietary protein from terrestrial animals, especially from large herbivores that roamed the open landscapes. Evidence based on the conventional carbon and nitrogen isotopic composition of bulk collagen has supported this view, although recent findings based on plant remains in the tooth calculus, microwear analyses, and small game and marine animal remains from archaeological sites have raised some questions regarding this assumption. However, the lack of a protein source other than meat in the Neanderthal diet may be due to methodological difficulties in defining the isotopic composition of plants. Based on the nitrogen isotopic composition of glutamic acid and phenylalanine in collagen for Neanderthals from Spy Cave (Belgium), we show that i) there was an inter individual dietary heterogeneity even within one archaeological site that has not been evident in bulk collagen isotopic compositions, ii) they occupied an ecological niche different from those of hyenas, and iii) they could rely on plants for up to similar to 20% of their protein source. These results are consistent with the evidence found of plant consumption by the Spy Neanderthals, suggesting a broader subsistence strategy than previously considered. (C) 2016 Elsevier Ltd. All rights reserved.
  • Arndt Schimmelrnann, Haiping Qi, Tyler B. Coplen, Willi A. Brand, Jon Fong, Wolfram Meier-Augenstein, Helen F. Kemp, Blaza Toman, Annika Ackermann, Sergey Assonov, Anita T. Aerts-Bijma, Ramona Brejcha, Yoshito Chikaraishi, Tamim Darwish, Martin Elsner, Matthias Gehre, Heike Geilmann, Manfred Groeing, Jean-Francois Helie, Sara Herrero-Martin, Harro A. J. Meijer, Peter E. Sauer, Alex L. Sessions, Roland A. Werner
    ANALYTICAL CHEMISTRY 88 8 4294 - 4302 2016年04月 [査読有り][通常論文]
     
    An international project developed, quality-tested, and determined isotope-delta values of 19 new organic reference materials (RMs) for hydrogen, carbon, and nitrogen stable isotope-ratio measurements, in addition to analyzing pre-existing RMs NBS 22 (oil), IAEA-CH-7 (polyethylene foil), and IAEA-600 (caffeine). These new RMs enable users to normalize measurements of samples to isotope-delta scales. The RMs span a range of delta H-2(VSMOW-SLAP) values from -210.8 to +397.0 mUr or parts per thousand, for delta C-13(VPDB-LSVEC) from -40.81 to +0.49 mUr and for delta N-15(Air) from -5.21 to +61.53 mUr. Many of the new RMs are amenable to gas and liquid chromatography. The RMs include triads of isotopically contrasting caffeines, C-16 n-alkanes, n-C-20-fatty acid methyl esters (FAMEs), glycines, and L-valines, together with polyethylene powder and string, one n-C-17-FAME, a vacuum oil (NBS 22a) to replace NBS 22 oil, and a H-2-enriched vacuum oil. A total of 11 laboratories from 7 countries used multiple analytical approaches and instrumentation for 2-point isotopic normalization against international primary measurement standards. The use of reference waters in silver tubes allowed direct normalization of delta H-2 values of organic materials against isotopic reference waters following the principle of identical treatment. Bayesian statistical analysis yielded the mean values reported here. New RMs are numbered from USGS61 through USGS78, in addition to NBS 22a. Because of exchangeable hydrogen, amino acid RMs currently are recommended only for carbon- and nitrogen-isotope measurements. Some amino acids contain C-13 and carbon-bound organic H-2-enrichments at different molecular sites to provide RMs for potential site-specific isotopic analysis in future studies.
  • Yuichi I. Naito, Hervé Bocherens, Yoshito Chikaraishi, Dorothée G. Drucker, Christoph Wißing, Minoru Yoneda, Naohiko Ohkouchi
    Journal of Archaeological Science: Reports 6 720 - 732 2016年04月 [査読有り][通常論文]
     
    © 2015 Elsevier Ltd. The detection of aquatic resource consumption is important in paleodietary studies as it provides insights into the adaptive strategies of modern humans. Debate as to whether or not it is a recent innovation in hominid evolution also emphasizes its importance to the field. Stable carbon and nitrogen isotope analysis of bulk collagen has been powerful tool for the investigation of ancient human diet, especially for the detection of marine food consumption. However, the nitrogen isotopic composition could significantly vary even within the same animal species depending on environmental conditions, making a dietary reconstruction based on human remains difficult without enough specimens of referential animal prey. Nitrogen isotope analysis of individual amino acids in bone collagen has recently been proposed as a potentially useful technique for the detection of not only marine resources in diets but also freshwater ones. In this paper, we further test its applicability to human populations in a variety of regions and chronological time periods in the world. We found that: (i) irrespective of climatic conditions, nitrogen isotopic compositions of glutamic acid and phenylalanine of terrestrial animals group similarly; (ii) these two amino acids are particularly useful to detect marine or freshwater resource consumption; (iii) a multinomial logistic regression based on some combinations of isotope indicators successfully distinguishes aquatic and terrestrial animals; (iv) detection of aquatic resource consumption by prehistoric humans could be possible based solely on the isotopic compositions of human remains, even in the absence of coeval potential prey. This approach is therefore promising for the paleodietary reconstruction of isolated human remains with few associated faunal remains from archaeological sites.
  • 高野 淑識, 力石 嘉人, 大河内 直彦
    Researches in Organic Geochemistry 32 1 1 - 18 日本有機地球化学会 2016年 [査読有り][通常論文]
     

    We report an analytical procedure of gas chromatography / mass spectrometry (GC / MS) focusing on chromatographic enantiomer separations and the corresponding mass spectra. We used N-pivaloyl isobutyl esters of amino acids to show the summary of retention time and those of mass fragmentation patters. To avoid matrix effect from biogeochemical samples, we optimized the entire experimental flow showing an optional wet chemical treatment for the purification of amino acids. We separated both of protein and non-protein type amino acids derived from the samples, including prokaryotic soft-tissues, freshwater / marine biological hard-tissues, and a deep-sea serpentine sample. Present derivatization procedures of amino acids as pivaloyl / isobutyl esters can be switchable on the diastereomers with the use of S-(+)-2-butyl esters or R-(-)-2-butyl esters. The present method will be applied into a further description of enantiomer-specific isotopic composition of individual amino acid.

  • Kruger, B.R, Werne, J.P, Branstrator, D.K, Hrabik, T.R, Chikaraishi, Y, Ohkouchi, N, Minor, E.C
    Limnology and Oceanography 61 1 149 - 164 2016年 [査読有り][通常論文]
  • Queenie Hoi Shan Chan, Yoshito Chikaraishi, Yoshinori Takano, Nanako O. Ogawa, Naohiko Ohkouchi
    EARTH PLANETS AND SPACE 68 2016年01月 [査読有り][通常論文]
     
    A novel method has been developed for compound-specific nitrogen isotope compositions with an achiral column which was previously shown to offer high precision for nitrogen isotopic analysis. We applied the method to determine the amino acid contents and stable nitrogen isotopic compositions of individual amino acids from the thermally metamorphosed (above 500 degrees C) Antarctic carbonaceous chondrites Ivuna-like (CI) 1 (or CI-like) Yamato (Y) 980115 and Ornans-like (CO) 3.5 Allan Hills (ALH) A77003 with the use of gas chromatography/combustion/isotope ratio mass spectrometry. ALHA77003 was deprived of amino acids due to its extended thermal alteration history. Amino acids were unambiguously identified in Y-980115, and the delta N-15 values of selected amino acids (glycine +144.8 %; alpha-alanine + 121.2%) are clearly extraterrestrial. Y-980115 has experienced an extended period of aqueous alteration as indicated by the presence of hydrous mineral phases. It has also been exposed to at least one post-hydration short-lived thermal metamorphism. Glycine and alanine were possibly produced shortly after the accretion event of the asteroid parent body during the course of an extensive aqueous alteration event and have abstained from the short-term post-aqueous alteration heating due to the heterogeneity of the parent body composition and porosity. These carbonaceous chondrite samples are good analogs that offer important insights into the target asteroid Ryugu of the Hayabusa-2 mission, which is a C-type asteroid likely composed of heterogeneous materials including hydrated and dehydrated minerals.
  • Shawn A. Steffan, Yoshito Chikaraishi, David R. Horton, Eugene Miliczky, Juan E. Zalapa, Vincent P. Jones, Naohiko Ohkouchi
    BIOLOGICAL CONTROL 91 34 - 41 2015年12月 [査読有り][通常論文]
     
    Carnivores indirectly protect plants by reducing herbivory. This important ecosystem service can be undermined, however, as carnivores feed upon fellow carnivores. Such intraguild predation is exceedingly common, yet measurement of the degree to which this occurs has remained elusive due to difficulties in measuring the trophic tendencies of free-roaming animals. Conventional molecular methods, such as bulk-isotopic analyses, do not produce reliably accurate trophic position estimates, and often the inaccuracy is substantial. With the advent of compound-specific isotopic analysis (CSIA), it is now possible to accurately quantify the lifetime trophic tendencies of wild carnivore populations. Unfortunately, CSIA is extraordinarily expensive and time-consuming, limiting the number of samples that can be analyzed. The need for high-quality trophic information has to be balanced with the inaccessibility of CSIA. Here, we propose coupling CSIA-derived trophic position estimates with conventional bulk-N-15 analysis, effectively calibrating site-specific bulk-N-15 data and thereby allowing for trophic position estimation using bulk data alone. We also create a framework that uses trophic position as a basis to characterize carnivores as beneficial for crop protection. Within an agricultural field, we demonstrated the utility of this new approach by measuring the trophic positions of six common arthropod species. We then compare these trophic position estimates to those deriving from conventional bulk-N-15 analysis. Our hybrid approach produced more accurate trophic position estimates than the stand-alone bulk-N-15 method. Ultimately, we were able to examine enough specimens to determine which carnivore populations were likely beneficial for plant protection, and which were not. Published by Elsevier Inc.
  • Shawn A. Steffan, Yoshito Chikaraishi, Cameron R. Currie, Heidi Horn, Hannah R. Gaines-Day, Jonathan N. Pauli, Juan E. Zalapa, Naohiko Ohkouchi
    PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA 112 49 15119 - 15124 2015年12月 [査読有り][通常論文]
     
    In most ecosystems, microbes are the dominant consumers, commandeering much of the heterotrophic biomass circulating through food webs. Characterizing functional diversity within the microbiome, therefore, is critical to understanding ecosystem functioning, particularly in an era of global biodiversity loss. Using isotopic fingerprinting, we investigated the trophic positions of a broad diversity of heterotrophic organisms. Specifically, we examined the naturally occurring stable isotopes of nitrogen (N-15: N-14) within amino acids extracted from proteobacteria, actinomycetes, ascomycetes, and basidiomycetes, as well as from vertebrate and invertebrate macrofauna (crustaceans, fish, insects, and mammals). Here, we report that patterns of intertrophic N-15-discrimination were remarkably similar among bacteria, fungi, and animals, which permitted unambiguous measurement of consumer trophic position, independent of phylogeny or ecosystem type. The observed similarities among bacterial, fungal, and animal consumers suggest that within a trophic hierarchy, microbiota are equivalent to, and can be interdigitated with, macrobiota. To further test the universality of this finding, we examined Neotropical fungus gardens, communities in which bacteria, fungi, and animals are entwined in an ancient, quadripartite symbiosis. We reveal that this symbiosis is a discrete four-level food chain, wherein bacteria function as the apex carnivores, animals and fungi are meso-consumers, and the sole herbivores are fungi. Together, our findings demonstrate that bacteria, fungi, and animals can be integrated within a food chain, effectively uniting the macro-and microbiome in food web ecology and facilitating greater inclusion of the microbiome in studies of functional diversity.
  • Hidetaka Nomaki, Yoshito Chikaraishi, Masashi Tsuchiya, Takashi Toyofuku, Hisami Suga, Yoko Sasaki, Katsuyuki Uematsu, Akihiro Tame, Naohiko Ohkouchi
    LIMNOLOGY AND OCEANOGRAPHY 60 6 1906 - 1916 2015年11月 [査読有り][通常論文]
     
    We evaluated nitrate utilization by benthic foraminifera at the redox boundary around the sediment-water interface by examining the stable nitrogen isotopic composition (N-15, parts per thousand vs. AIR) of amino acids. Five foraminiferal species collected from bathyal Sagami Bay (water depth, 1430m) in three different sampling seasons were analyzed by determining the N-15 values of amino acids from whole cells and those in test (shell) proteins remaining after H2O2 treatment. The N-15 values of phenylalanine fell within a narrow range (typically 1-3 parts per thousand) in the test proteins of all five species, but the whole-cell N-15 values of phenylalanine were substantially different from those of the test proteins in two species, Globobulimina affinis (by 6.3 parts per thousand) and Uvigerina akitaensis (by 4.5 parts per thousand). These differences in the N-15 values of amino acids suggest that these species utilize nitrate in their cells probably for nitrate respiration (i.e., denitrification) to adapt to oxygen-depleted environments, as was previously observed in the shallow water benthic foraminifera Ammonia sp. Apparent trophic positions determined using the N-15 values of amino acids also differed between whole cells and tests in G. affinis, U. akitaensis, and Ammonia sp., perhaps because they have different microbial associations, as observed by cellular ultrastructural analysis. These differences in nitrate utilization and microbial associations among benthic foraminifera suggest that foraminifera adapt in diverse ways to conditions in dysoxic to anoxic sediments.
  • Shunsaku Miyachi, Takeyuki Mayahara, Kouji Tsushima, Katsuhiro Sasada, Eiichi Kohno, Nanako O. Ogawa, Yoshito Chikaraishi, Naohiko Ohkouchi
    FISHERIES SCIENCE 81 6 1053 - 1062 2015年11月 [査読有り][通常論文]
     
    Compound-specific stable isotope analysis of amino acids (AA method) has recently been used to estimate the trophic level (TL) of animals. The individual TL (TLGlu/Phe) of Japanese anchovy Engraulis japonicus was precisely determined using the AA method without sampling or analysis of primary producers. Previously, TLs of organisms were determined using bulk nitrogen stable isotopic composition (delta N-15(bulk)) of tissues (bulk method). The delta N-15(bulk) for Japanese anchovies varied widely because of their migratory behavior, and the TL of anchovies in Sagami Bay remained ambiguous. We showed that the TLGlu/Phe of anchovy was almost 3 and that food-web structures differed between inshore and offshore waters. Furthermore, there was little difference in TLGlu/Phe for representative Japanese anchovies in Sagami Bay, despite the large intra-sample variation in delta N-15(bulk) for anchovies ranging over a trophic shift of 3-4 aEuro degrees in Sagami Bay. We speculated that this variation in delta N-15(bulk) resulted from differences in food sources among the different food webs. Estimation of individual TLs in some simple food chains using the AA method may enable the determination of the food-web structure of migratory fishes, which is difficult to determine using the traditional bulk method.
  • Toshiro Yamanaka, Sho Shimamura, Yoshito Chikaraishi, Takuma Haga, Yoshihiro Fujiwara
    MARINE ECOLOGY PROGRESS SERIES 540 157 - 165 2015年11月 [査読有り][通常論文]
     
    Wood-boring bivalves (families Xylophagaidae and Teredinidae) are unique bivalves that are peculiarly adapted to feed on terrigenous woody materials, even though they inhabit the deep-sea floor far from land. Previous studies of their metabolic processes suggested the importance of symbiotic microbes that secrete cellulase to access woody carbon (carbohydrates), and supply organic nitrogen via nitrogen fixation. Since nitrogen is generally depleted in woody materials, dissolved dinitrogen in seawater has been proposed as a plausible nitrogen source for wood-boring bivalves. We evaluated the food ecology of wood-boring bivalves (genus: Xyloredo) obtained from the deep seafloor off the Ryukyu Islands by considering their bulk carbon, nitrogen, and sulfur isotope composition and potential dietary sources (i.e. logs, particulate organic matter, and surface sediments). We also investigated the trophic interactions between wood-boring bivalves and logs based on the amino acid nitrogen isotopic composition. The bulk isotope data revealed that in wood-boring bivalves these elements are derived mainly from the logs in which they live. These results were consistent with the trophic hierarchy calculated from the nitrogen isotopic composition of amino acids. Ecologically, wood-boring bivalves are one step higher than logs in terms of their trophic position. Based on these data, we propose that terrigenous woody materials are the major dietary sources for wood-boring bivalves and the same standard trophic interaction exists between diet and consumer species as in the grazing food web. The symbionts may aid the digestion of woody materials, but they do not supply nitrogen via nitrogen fixation in this case.
  • Svenja Kruse, Evgeny A. Pakhomov, Brian P. V. Hunt, Yoshito Chikaraishi, Nanako O. Ogawa, Ulrich Bathmann
    MARINE ECOLOGY PROGRESS SERIES 529 63 - 74 2015年06月 [査読有り][通常論文]
     
    Trophic dynamics of 2 abundant macrozooplankton species Salpa thompsoni and Themisto gaudichaudii were studied during the austral summer at 2 locations near the Antarctic Polar Front with contrasting low and high chlorophyll a (chl a) concentrations. Compound-specific stable isotope analysis, complemented by gut content and bulk isotope analyses, were used to investigate trophic interactions between species, and to assess their trophic positions in the pelagic food web. The results of the compound-specific stable isotope analysis placed S. thompsoni at the second trophic level and approx. 1 trophic level below T. gaudichaudii. Two forms of T. gaudichaudii appeared to feed at different trophic levels, with T. gaudichaudii bispinosa feeding at a higher trophic level (similar to 3.3) than T. gaudichaudii compressa (similar to 2.8). Isotope data coupled with gut content analysis indicated a regular consumption of salps in both areas, although a higher contribution of gelatinous prey was encountered in a chl a poor area. The food web baseline values (bulk delta C-13) varied regionally, highlighting 2 independent food webs albeit with a similar trophic structure. Overall, our findings suggested that in areas where S. thompsoni is highly abundant, T. gaudichaudii may be a significant predator of this species.
  • Yoshito Chikaraishi, Shawn A. Steffan, Yoshinori Takano, Naohiko Ohkouchi
    ECOLOGY AND EVOLUTION 5 10 2048 - 2059 2015年05月 [査読有り][通常論文]
     
    Stable nitrogen isotopic composition of amino acids (N-15(AA)) has recently been employed as a powerful tool in ecological food web studies, particularly for estimating the trophic position (TP) of animal species in food webs. However, the validity of these estimates depends on the consistency of the trophic discrimination factor (TDF; = N-15(AA) at each shift of trophic level) among a suite of amino acids within the tissues of consumer species. In this study, we determined the TDF values of amino acids in tadpoles (the Japanese toad, Bufo japonicus) reared exclusively on one of three diets that differed in nutritional quality. The diets were commercial fish-food pellets (plant and animal biomass), bloodworms (animal biomass), and boiled white rice (plant carbohydrate), representing a balanced, protein-rich, and protein-poor diet, respectively. The TDF values of two source amino acids (Src-AAs), methionine and phenylalanine, were close to zero (0.3-0.5 parts per thousand) among the three diets, typifying the values reported in the literature (similar to 0.5 parts per thousand and similar to 0.4 parts per thousand, respectively). However, TDF values of trophic amino acids (Tr-AAs) including alanine, valine, leucine, isoleucine, and glutamic acid varied by diet: for example, the glutamic acid TDF was similar to the standard value (similar to 8.0 parts per thousand) when tadpoles were fed either the commercial pellets (8.0 parts per thousand) or bloodworms (7.9 parts per thousand), but when they were fed boiled rice, the TDF was significantly reduced (0.6 parts per thousand). These results suggest that a profound lack of dietary protein may alter the TDF values of glutamic acid (and other Tr-AAs and glycine) within consumer species, but not the two Src-AAs (i.e., methionine and phenylalanine). Knowledge of how a nutritionally poor diet can influence the TDF of Tr- and Src-AAs will allow amino acid isotopic analyses to better estimate TP among free-roaming animals.
  • Yoshinori Takano, Yoshito Chikaraishi, Naohiko Ohkouchi
    INTERNATIONAL JOURNAL OF MASS SPECTROMETRY 379 16 - 25 2015年03月 [査読有り][通常論文]
     
    Nitrogen isotopic composition of amino acids has been widely applied to biochemical, ecological, archeological, and biogeochemical studies in an attempt to trace nitrogen source and transformation processes. For accurate isotope analysis of individual amino acids, we validated a preparative method involving the isolation of underivatized amino acids by ion-pair chromatographic separation and confirmed the consistency of nitrogen isotope composition. Ion-pair reversed-phase liquid chromatography coupled with electrospray ionization mass spectrometry (LC/ESI-MS) and gas chromatography/combustion coupled with isotope ratio mass spectrometry (GC/C/IRMS) were conducted for the purpose of separation of underivatized amino acids and nitrogen isotopic analysis, respectively. Firstly, we confirmed the resolution of proteinogenic and non-proteinogenic amino acids by the preparative ion-pair LC separation. Diagnostic product ions determined by mass spectrometry can support the rapid identification of individual amino acids in screening analyses. Secondly, we observed no dependency on nitrogen isotopic composition for the injection amount of underivatized amino acids and even for different chemical formula including neutral, acidic, sulfur-containing, heterocyclic, and aromatic species. The recovery during the LC was 91.7 +/- 4.3% (n = 3). The present method and strategy of LC coupled with GC/C/IRMS (i.e., comprehensive LC x GC/C/IRMS) are useful for the high precision determination of the nitrogen isotopic composition of amino acids, in conjunction with an appropriate pre-treatment of cation-exchange chromatographic procedures. (C) 2014 The Authors. Published by Elsevier B.V.
  • Naohiko Ohkouchi, Nanako O. Ogawa, Yoshito Chikaraishi, Hiroyuki Tanaka, Eitaro Wada
    PROGRESS IN EARTH AND PLANETARY SCIENCE 2 2015年02月 [査読有り][通常論文]
     
    We review the biochemical and physiological bases of the use of carbon and nitrogen isotopic compositions as an approach for environmental and ecological studies. Biochemical processes commonly observed in the biosphere, including the decarboxylation and deamination of amino acids, are the key factors in this isotopic approach. The principles drawn from the isotopic distributions disentangle the complex dynamics of the biosphere and allow the interactions between the geosphere and biosphere to be analyzed in detail. We also summarize two recently examined topics with new datasets: the isotopic compositions of individual biosynthetic products ( chlorophylls and amino acids) and those of animal organs for further pursuing the basis of the methodology. As a tool for investigating complex systems, compound-specific isotopic analysis compensates the intrinsic disadvantages of bulk isotopic signatures. Chlorophylls provide information about the particular processes of various photoautotrophs, whereas amino acids provide a precise measure of the trophic positions of heterotrophs. The isotopic distributions of carbon and nitrogen in a single organism as well as in the whole biosphere are strongly regulated, so that their major components such as amino acids are coordinated appropriately rather than controlled separately.
  • Hidetaka Nomaki, Yoshito Chikaraishi, Masashi Tsuchiya, Takashi Toyofuku, Hisami Suga, Yoko Sasaki, Katsuyuki Uematsu, Akihiro Tame, Naohiko Ohkouchi
    Limnology and Oceanography 60 6 1906 - 1916 2015年 [査読有り][通常論文]
     
    We evaluated nitrate utilization by benthic foraminifera at the redox boundary around the sediment-water interface by examining the stable nitrogen isotopic composition (δ15N, ‰ vs. AIR) of amino acids. Five foraminiferal species collected from bathyal Sagami Bay (water depth, 1430 m) in three different sampling seasons were analyzed by determining the δ15N values of amino acids from whole cells and those in test (shell) proteins remaining after H2O2 treatment. The δ15N values of phenylalanine fell within a narrow range (typically 1-3 ‰) in the test proteins of all five species, but the whole-cell d δ15N values of phenylalanine were substantially different from those of the test proteins in two species, Globobulimina affinis (by 6.3 ‰)and Uvigerina akitaensis (by 4.5 ‰). These differences in the δ15N values of amino acids suggest that these species utilize nitrate in their cells probably for nitrate respiration (i.e., denitrification) to adapt to oxygen-depleted environments, as was previously observed in the shallow water benthic foraminifera Ammonia sp. Apparent trophic positions determined using the δ15N values of amino acids also differed between whole cells and tests in G. affinis, U. akitaensis,and Ammonia sp., perhaps because they have different microbial associations, as observed by cellular ultrastructural analysis. These differences in nitrate utilization and microbial associations among benthic foraminifera suggest that foraminifera adapt in diverse ways to conditions in dysoxic to anoxic sediments.
  • 安定同位体分析による北西太平洋におけるカタクチイワシとマイワシの栄養段階と食源の推定.
    宮地 俊作, 馬谷原 武之, 對馬 孝治, 笹田 勝寛, 河野 英一, 川端 淳, 力石 嘉人, 小川 奈々子, 大河内 直彦
    日本生物地理学会会報 70 33 - 41 2015年 [査読有り][通常論文]
  • 高野 淑識, 力石 嘉人, 大河内 直彦
    Researches in Organic Geochemistry 31 1 33 - 49 2015年 [査読有り][通常論文]
  • Researches in Organic Geochemistry
    Researches in organic geochemistry 30 1 29 - 32 日本有機地球化学会 2014年12月 [査読有り][通常論文]
     
    Sweet potatoes sometimes sprout the purple color of stems with several small leaves in the house pantry. In the present study, we investigated the trophic hierarchy between a mother sweet potato and its baby sprouts grown without any light in a dark house pantry, based on stable nitrogen isotopic composition (δ^<15>N,‰ vs. AIR) of glutamic acid and phenylalanine. The isotope data reveal that glutamic acid has a significant ^<15>N-enrichment (by 6.9‰) from the mother sweet potato to its baby sprout while phenylalanine has a little ^<15>5N-enrichment (by 0.6‰) between them. Interestingly, the isotopic heterogeneity found within the sweet potato is very similar to the isotopic discrimination generally found in the combination between plants and herbivores during grazing food webs (ca. 8.0‰ for glutamic acid and ca. 0.4‰ for phenylalanine). These results suggest that the proteins in the mother sweet potatoes are major resources for not only proteins in their baby sprouts but also growth energy in the sprouting, when they are grown heterotrophically without any light.
  • Hidetaka Nomaki, Yoshito Chikaraishi, Masashi Tsuchiya, Takashi Toyofuku, Naohiko Ohkouchi, Katsuyuki Uematsu, Akihiro Tame, Hiroshi Kitazato
    LIMNOLOGY AND OCEANOGRAPHY 59 6 1879 - 1888 2014年11月 [査読有り][通常論文]
     
    Among eukaryotes, some benthic foraminiferal species have been reported to be capable of nitrate respiration, although little is known about their denitrification processes. In this study, we incubated the shallow-water benthic foraminifer Ammonia beccarii with isotopically labeled sodium nitrate (-73 parts per thousand, 0 parts per thousand, or +73 parts per thousand) under oxic or anoxic conditions to investigate how nitrate is used in foraminiferal cells and whether those signatures remain in amino acids. The delta N-15 values of amino acids from bulk cells incubated under anoxic conditions were correlated with those of nitrate in seawater and were enriched in N-15 by up to, similar to 50% compared to the isotopic compositions in seawater. There was no such relationship or enrichment in the cases of organic matter in the calcite tests under oxic or anoxic conditions or bulk cells under oxic conditions, suggesting that benthic foraminifera take up ambient nitrate under anoxic conditions and use it for denitrification; the remaining N-15-enriched intracellular nitrate pool is used for amino acid synthesis, probably by endosymbiotic microbes, as suggested by observation of the cellular ultrastructure. The degree of N-15 enrichment may depend on denitrification rates of the intracellular nitrate pool. Because the amino acids in the calcite test are synthesized by foraminifera, they were not enriched in N-15, even under anoxic conditions. Thus, differences between amino acid delta N-15 of bulk foraminiferal cells and organic matter in tests may serve as a proxy for denitrification in foraminiferal cells and microbial amino acid synthesis under oxygen-depleted conditions.
  • K. Maki, N. Ohkouchi, Y. Chikaraishi, H. Fukuda, T. Miyajima, T. Nagata
    GEOCHIMICA ET COSMOCHIMICA ACTA 140 521 - 530 2014年09月 [査読有り][通常論文]
     
    Nitrogen (N) isotopic compositions of individual hydrolysable amino acids (delta N-15(AAs)) in N pools have been increasingly used for trophic position assessment and evaluation of sources and transformation processes of organic matter in marine environments. However, there are limited data about variability in delta N-15(AAs) patterns and how this variability influences marine bacteria, an important mediator of trophic transfer and organic matter transformation. We explored whether marine bacterial delta N-15(AAs) profiles change depending on the type and C: N ratio of the substrate. The delta N-15(AAs) profile of a marine bacterium, Vibrio harveyi, was examined using medium containing either glutamate, alanine or ammonium as the N source [substrate C:N ratios (range, 3 to 20) were adjusted with glucose]. The data were interpreted as a reflection of isotope fractionations associated with de novo synthesis of amino acids by bacteria. Principal component analysis (PCA) using the delta N-15 offset values normalized to glutamate + glutamine delta N-15 revealed that delta N-15(AAs) profiles differed depending on the N source and C:N ratio of the substrate. High variability in the delta N-15 offset of alanine and valine largely explained this bacterial delta N-15(AAs) profile variability. PCA was also conducted using bacterial and phytoplankton (cyanobacteria and eukaryotic algae) delta N-15(AAs) profile data reported previously. The results revealed that bacterial delta N-15(AAs) patterns were distinct from those of phytoplankton. Therefore, the delta N-15(AAs) profile is a useful indicator of biochemical responses of bacteria to changes in substrate conditions, serving as a potentially useful method for identifying organic matter sources in marine environments. (C) 2014 The Authors. Published by Elsevier Ltd.
  • Yoshito Chikaraishi, Shawn A. Steffan, Nanako O. Ogawa, Naoto F. Ishikawa, Yoko Sasaki, Masashi Tsuchiya, Naohiko Ohkouchi
    ECOLOGY AND EVOLUTION 4 12 2423 - 2449 2014年06月 [査読有り][通常論文]
     
    Food webs are known to have myriad trophic links between resource and consumer species. While herbivores have well-understood trophic tendencies, the difficulties associated with characterizing the trophic positions of higher-order consumers have remained a major problem in food web ecology. To better understand trophic linkages in food webs, analysis of the stable nitrogen isotopic composition of amino acids has been introduced as a potential means of providing accurate trophic position estimates. In the present study, we employ this method to estimate the trophic positions of 200 free-roaming organisms, representing 39 species in coastal marine (a stony shore) and 38 species in terrestrial (a fruit farm) environments. Based on the trophic positions from the isotopic composition of amino acids, we are able to resolve the trophic structure of these complex food webs. Our approach reveals a high degree of trophic omnivory (i.e., noninteger trophic positions) among carnivorous species such as marine fish and terrestrial hornets. This information not only clarifies the trophic tendencies of species within their respective communities, but also suggests that trophic omnivory may be common in these webs.
  • Rie Sato, Hidehiko Kawanishi, Arnd Schimmelmann, Yaeko Suzuki, Yoshito Chikaraishi
    BUNSEKI KAGAKU 63 5 399 - 403 2014年05月 [査読有り][通常論文]
     
    The availability of suitable standards (i.e., internationally calibrated reference materials) is a common issue as an analytical chemical precondition accurately measuring stable isotope ratios in many scientific disciplines. However, the traditional IAEA and NIST standards are in limited supply, particularly for the isotope analysis of organic hydrogen (D/H), carbon ((13)c/(12)c,) nitrogen (N-15/N-14), oxygen (O-18/O-16), and sulfur (S-34/S-32). In a subproject coupled with the international project "Development of Organic H, C, and N Stable Isotope International Standards for NIST and IAEA", we recently produced new reference materials of nine amino acids. These reference martials were designed as a working standard set to cover the naturally occurring nitrogen isotopic heterogeneity, ranging from -25 to +45 %o (delta N-15 value, vs. Air), which would be useful as the first internationally suitable reference materials for modern applications of the nitrogen isotope analysis of amino acids and other nitrogenous organic compounds.
  • Masanori Kaneko, Yoshinori Takano, Yoshito Chikaraishi, Nanako O. Ogawa, Susumu Asakawa, Takeshi Watanabe, Seigo Shima, Martin Krueger, Makoto Matsushita, Hiroyuki Kimura, Naohiko Ohkouchi
    ANALYTICAL CHEMISTRY 86 7 3633 - 3638 2014年04月 [査読有り][通常論文]
     
    Coenzyme F430 is a nickel hydrocorphinoid and is the prosthetic group of methyl coenzyme M reductase that catalyzes the last step of the methanogenic reaction sequence and its reversed reaction for anaerobic methane oxidation by ANME. As such, function-specific compound analysis has the potential to reveal the microbial distribution and activity associated with methane production and consumption in natural environments and, in particular, in deep subsurface sediments where microbiological and geochemical techniques are restricted. Herein, we report the development of a technique for high-sensitivity analysis of F430 in environmental samples, including paddy soils, marine sediments, microbial mats, and an anaerobic groundwater. The lower detection limit of F430 analysis by liquid chromatography/mass spectrometry is 0.1 femto mol, which corresponds to 6 x 10(2) to 1 x 10(4) cells of methanogens. F430 concentrations in these natural environmental samples range from 63 X 10(-6) to 44 nmol g(-1) and are consistent with the methanogenic archaeal biomass estimated by microbiological analyses.
  • Kyoko Kamata, Yoshito Chikaraishi
    BUNSEKI KAGAKU 63 3 279 - 282 2014年03月 [査読有り][通常論文]
     
    Compound-specific stable isotope analysis (CSIA) of nitrogenous compounds has been carried out by using a gas chromatography/isotope ratio mass spectrometry (GC/IRMS) system, which traditionally includes two separate conversion processes: the oxidation of nitrogenous compounds to N-2 and NOX; and the reduction of the NOX to N-2. However, the last major update of the GC/IRMS instrument combined these two processes into one unit by introducing a high-temperature combustion reactor. However, few studies have evaluated the applicability of this new GC/IRMS system to measuring the nitrogen isotopic composition of compounds of interest. In the present study, we determined the nitrogen isotopic composition of ten amino acids by this new GC/IRMS system, and obtained the isotopic composition with 0.6 parts per thousand for accuracy (mean of Delta) and 1.2 parts per thousand for precision (mean of 1 sigma). These results suggest that the new GC/IRMS system is basically applicable to the CSIA of nitrogenous compounds, and also that further optimization is required for reducing the analytical error to that of the traditional GC/IRMS system (ca. 0.0 parts per thousand for accuracy and 0.4-0.7 parts per thousand for precision).
  • 力石 嘉人, 高野 淑識, 大河内 直彦
    日本地球化学会年会要旨集 61 23 - 23 日本地球化学会 2014年 
    本研究では,インゲン(C3植物)とトウモロコシ(C4植物)の苗の土壌に0.1mMの13C-15Nロイシン水溶液100mLを与え,苗葉中のアミノ酸の13C,15N濃度の変化を調べた。その結果,(1) C3植物では土壌アミノ酸の直接的な摂取が行われていないことを確認し,また一方で,(2) C4植物はC3植物とは異なり,土壌中のアミノ酸を直接取り込み,それを利用する能力があることがわかった。
  • 大河内 直彦, 力石 嘉人
    日本地球化学会年会要旨集 61 24 - 24 日本地球化学会 2014年 
    タンパク質を構成しているアミノ酸の窒素安定同位体比は,栄養段階の指標として用いることができる。現在,海棲生物,陸上C3植物系,陸上C4植物系の3種類の式が知られており,いずれの応用例もこれまでの生態学で得られた知見と非常によく一致する。本講演では,この方法論を現代人の爪に応用し,現代人の食性解析を行った結果を報告する。測定対象となったのは,日本人だけでなく欧州や南北アメリカ大陸の人々から採取さいた試料である。さらに日本人については,マーケットで売られている肉,野菜,魚などの多数の食品についても分析し,それらとの関係について考察する。
  • Yu Itahashi, Yoshito Chikaraishi, Naohiko Ohkouchi, Minoru Yoneda
    GEOCHEMICAL JOURNAL 48 6 E15 - E19 2014年 [査読有り][通常論文]
     
    We determined the stable nitrogen isotopic composition (delta N-15) of amino acids in bone collagen from samples of three archaeological herbivores (cattle, sheep, and goats), collected from the Tell Ain el-Kerkh Neolithic site in Syria. Bulk collagen delta N-15 values exhibited significant differences between the three species (by up to 3.2 parts per thousand), and were strongly correlated with those of glycine (R-2 = 0.87), the most abundant amino acid in bone collagen. On the other hand, the delta N-15 values of two other minor amino acids (glutamic acid and phenylalanine) in the different samples were within narrow ranges (0.9 parts per thousand and 0.5 parts per thousand, respectively), and exhibited either weak or no correlation with those of bulk collagen. The trophic position estimated by the delta N-15 values of glutamic acid and phenylalanine (2.0 +/- 0.1) is consistent with that of herbivores. These results suggest that the delta N-15 values of bulk bone collagen may vary among herbivores, partly on account of their differing amino acid compositions, whereas the trophic position of different herbivores is faithfully preserved in the delta N-15 values of glutamic acid and phenylalanine.
  • Y. Chikaraishi
    Treatise on Geochemistry: Second Edition 12 95 - 123 2013年11月 [査読有り][通常論文]
     
    Two naturally occurring stable isotopes of carbon, 12C and 13C, are unevenly distributed among organic materials because of the isotopic fractionation in physical, chemical, and biological processes. This chapter reviews the carbon isotopic composition of biomass and biomolecules in plants and algae and summarizes the physical and enzymatic mechanisms of isotopic fractionation associated with photosynthetic and biosynthetic pathways. © 2014 Elsevier Ltd. All rights reserved.
  • Ogawa Nanako O, Chikaraishi Y, Ohkouchi N
    ECOLOGICAL RESEARCH 28 5 697 - 702 Springer Japan 2013年09月 [査読有り][通常論文]
  • Shawn A. Steffan, Yoshito Chikaraishi, David R. Horton, Naohiko Ohkouchi, Merritt E. Singleton, Eugene Miliczky, David B. Hogg, Vincent P. Jones
    PLOS ONE 8 9 2013年09月 [査読有り][通常論文]
     
    Food web ecologists have long sought to characterize the trophic niches of animals using stable isotopic analysis. However, distilling trophic position from isotopic composition has been difficult, largely because of the variability associated with trophic discrimination factors (inter-trophic isotopic fractionation and routing). We circumvented much of this variability using compound-specific isotopic analysis (CSIA). We examined the N-15 signatures of amino acids extracted from organisms reared in pure culture at four discrete trophic levels, across two model communities. We calculated the degree of enrichment at each trophic level and found there was a consistent trophic discrimination factor (similar to 7.6 parts per thousand). The constancy of the CSIA-derived discrimination factor permitted unprecedented accuracy in the measurement of animal trophic position. Conversely, trophic position estimates generated via bulk-N-15 analysis significantly underestimated trophic position, particularly among higher-order consumers. We then examined the trophic hierarchy of a free-roaming arthropod community, revealing the highest trophic position (5.07) and longest food chain ever reported using CSIA. High accuracy in trophic position estimation brings trophic function into sharper focus, providing greater resolution to the analysis of food webs.
  • Yuichi I. Naito, Yoshito Chikaraishi, Naohiko Ohkouchi, Dorothee G. Drucker, Herve Bocherens
    WORLD ARCHAEOLOGY 45 3 338 - 359 2013年08月 [査読有り][通常論文]
     
    Aquatic resource exploitations in human evolution have raised many questions related to cognitive abilities and subsistence developments. It has been pointed out that the evaluation of freshwater resource consumption based on conventional stable CN isotopic composition of bulk bone collagen faces some difficulties, primarily because isotopic distinction between terrestrial and freshwater animals can be ambiguous and, even worse, can show similar values. In this study we tested the potential of nitrogen isotope analysis of individual amino acids in this evaluation. Our preliminary results for archaeological human and faunal remains from Mesolithic and Epipalaeolithic sites in France (Noyen-sur-Seine and Pont d'Ambon) show that estimated trophic positions for terrestrial animals based on N-15 of glutamic acid and phenylalanine are more precise than the bulk collagen isotopic method, allowing human aquatic resource consumptions to be identified. However, since the ability to quantify is still limited, a combination of several approaches is recommended.
  • Yuichi I. Naito, Yoshito Chikaraishi, Naohiko Ohkouchi, Minoru Yoneda
    JOURNAL OF ARCHAEOLOGICAL SCIENCE 40 7 2913 - 2923 2013年07月 [査読有り][通常論文]
     
    Archaeological studies including stable carbon and nitrogen isotope analyses of bone collagen from human remains have suggested their heavy dependence on terrestrial foods during the Jomon period in the inland central region in Japan. However, it is not easy to quantitatively evaluate the extent of carnivory for archaeological human remains based on the bulk collagen chemistry, because of variable N-15-enrichment factor along the trophic step and background isotopic variations in ecosystems. In order to overcome these problems and more precisely evaluate diets of prehistoric humans who strongly adapted to terrestrial environment, in this study we applied nitrogen isotope analysis of individual amino acids in bone collagen to two inland human populations in the Jomon period. Our results suggest that the two populations were predominantly dependent on the C-3-plant-based terrestrial ecosystem and consumed little aquatic resources. Furthermore, their mean trophic positions (2.7 for both cases) are closer to that of the fox (2.8-3.0) rather than those of pure herbivores (2.0-2.2), and show little change over time. These results are the first evidence that inland Jomon populations may have had more carnivorous diets than is traditionally considered. (C) 2013 Elsevier Ltd. All rights reserved.
  • Naohiko Ohkouchi, Ryuichi Tsuda, Yoshito Chikaraishi, Kazushige Tanabe
    MARINE BIOLOGY 160 4 773 - 779 2013年04月 [査読有り][通常論文]
     
    The ram's horn squid, Spirula spirula (Spirulida, Coleoidea), inhabits subsurface waters of the tropical and subtropical oceans. Because of the presence of an internal chambered shell in this species, it has frequently been used as a model species to investigate the paleobiology of fossil coleoids. However, the feeding and dietary habits of S. spirula in the nature are poorly known. In this study, we applied a new method (amino acid nitrogen isotopic analysis) to estimate the trophic position of S. spirula specimens captured off Suriname, as well as three cuttlefish Sepia species (Sepia officinalis, S. latimanus, and S. esculenta), with a calcified chambered shell from the shallower water. The trophic position of S. spirula was estimated to be 2.5-2.8, which was significantly lower than that for the three Sepia species (3.4-3.6). The results and available data on the gastric contents of S. spirula suggest that it feeds mainly on detritus and zooplankton, including crustaceans, from the overlying water column. The method used in this study can potentially be applied to the estimation of the trophic position of the fossil cephalopods having calcified chambered shells.
  • Hiromi Watanabe, Eriko Seo, Yoshimi Takahashi, Takao Yoshida, Shigeaki Kojima, Katsunori Fujikura, Hiroshi Miyake
    JOURNAL OF OCEANOGRAPHY 69 1 129 - 134 2013年02月 [査読有り][通常論文]
     
    Vesicomyid bivalves have a substantial biomass in deep-sea chemosynthetic biological communities in the Pacific. Using a novel multiplex-PCR (mPCR) method to identify the co-occurring vesicomyids in Sagami Bay, we analyzed the distribution of Calyptogena okutanii and Calyptogena soyoae along environmental gradients. All the known distributions of C. okutanii indicated the different preferences in salinity and temperature to those of C. soyoae, and in Sagami Bay, depth seemed to be an important environmental factor, too. Although the concentration of hydrogen sulfide in sediment was not examined, our results showed that the distributions of these two Calyptogena clams were affected by salinity and temperature.
  • Michael J. Miller, Yoshito Chikaraishi, Nanako O. Ogawa, Yoshiaki Yamada, Katsumi Tsukamoto, Naohiko Ohkouchi
    BIOLOGY LETTERS 9 1 2013年02月 [査読有り][通常論文]
     
    What eel larvae feed on in the surface layer of the ocean has remained mysterious. Gut contents and bulk nitrogen stable isotope studies suggested that these unusual larvae, called leptocephali, feed at a low level in the oceanic food web, whereas other types of evidence have suggested that small zooplankton are eaten. In this study, we determined the nitrogen isotopic composition of amino acids of both natural larvae and laboratory-reared larvae of the Japanese eel to estimate the trophic position (TP) of leptocephali. We observed a mean TP of 2.4 for natural leptocephali, which is consistent with feeding on particulate organic matter (POM) such as marine snow and discarded appendicularian houses containing bacteria, protozoans and other biological materials. The nitrogen isotope enrichment values of the reared larvae confirm that the primary food source of natural larvae is consistent only with POM. This shows that leptocephali feed on readily available particulate material originating from various sources closely linked to ocean primary production and that leptocephali are a previously unrecognized part of oceanic POM cycling.
  • Kanji Aoyagi, Akiko S. Goto, Tatsuya Fujino, Takashi Korenaga, Yoshito Chikaraishi
    Researches in Organic Geochemistry 29 65 - 69 日本有機地球化学会 2013年 [査読有り][通常論文]
     
    We examined stable hydrogen (δD, ‰ relative to V-SMOW) and carbon isotopic compositions (δ^<13>C, ‰ relative to V-PDB) of fatty acids extracted from beef, and compared them with those from feeds (mixtures of plant materials) for the cattle. The δD value of stearic acid in beef is similar to that in the feeds, whereas the palmitic and oleic acids in beef are both significantly depleted in D (by ca. 60‰) as compared with the corresponding acids in the feeds. On the other hand, these fatty acids in beef are enriched in ^<13>C (by up to 5.7‰) relative to the corresponding acids in the feeds. Thus, the isotopic compositions of fatty acids in beef are not identical to those in the feeds. These results suggest that fatty acids in beef are an admixture of fatty acids derived from de novo biosynthesis in the cattle and from the feeds, and may imply that a considerable D-depletion process (e.g., hydrogenation of feed-derived fatty acids and/or dehydrogenation-hydrogenation cycling) occur in the fatty acids of the cattle.
  • Yoshito Chikaraishi, Masanori Kaneko, Naohiko Ohkouchi
    GEOCHIMICA ET COSMOCHIMICA ACTA 111 78 - 87 2013年01月 [査読有り][通常論文]
     
    We report the molecular and stable isotopic (delta D and delta C-13) compositions of long-chain n-alkanes in common insects including the cabbage butterfly, swallowtail, wasp, hornet, grasshopper, and ladybug. Insect n-alkanes are potential candidates of the contamination of soil and sedimentary n-alkanes that are believed to be derived from vascular plant waxes. Long-chain n-alkanes (range C21-33; maximum C-23-C-29) are found to be abundant in the insects (31-781 mu g/dry g), with a carbon preference index (CPI) of 5.1-31.5 and an average chain length (ACL) of 24.9-29.3. The isotopic compositions (mean +/- 1 sigma, n = 33) of the n-alkanes are -195 +/- 16 parts per thousand for hydrogen and -30.6 +/- 2.4 parts per thousand for carbon. The insect n-alkanes are depleted in D by approximately 30-40 parts per thousand compared with wax n-alkanes from C3 (-155 +/- 25 parts per thousand) and C4 vascular plants (-167 +/- 13 parts per thousand), whereas their delta C-13 values fall between those of C3 (-36.2 +/- 2.4 parts per thousand) and C4 plants (-20.3 +/- 2.4 parts per thousand). Thus, the contribution of insect-derived n-alkanes to soil and sediment could potentially shift delta D records of n-alkanes toward more negative values and potentially muddle the assumed original C3/C4 balance in the delta C-13 records of the soil and sedimentary n-alkanes. n-Alkenes are also found in three insects (swallowtail, wasp and hornet). They are more depleted in D relative to the same carbon numbered n-alkanes (delta Dn-alkene - delta Dn-alkane = -17 +/- 16 parts per thousand), but the delta C-13 values are almost identical to those of the n-alkanes (delta C-13(n-alkene) - delta C-13(n-alkane) = 0.1 +/- 0.2 parts per thousand). These results suggest that these n-alkenes are desaturated products of the same carbon numbered n-alkanes. (C) 2012 Elsevier Ltd. All rights reserved.
  • Yoshito Chikaraishi, Masanori Kaneko, Naohiko Ohkouchi
    GEOCHIMICA ET COSMOCHIMICA ACTA 95 53 - 62 2012年10月 [査読有り][通常論文]
     
    We report the molecular and stable isotopic (delta D and delta C-13) compositions of long-chain n-alkanes in common insects including the cabbage butterfly, swallowtail, wasp, hornet, grasshopper, and ladybug. Insect n-alkanes are potential candidates of the contamination of soil and sedimentary n-alkanes that are believed to be derived from vascular plant waxes. Long-chain n-alkanes (range C21-33; maximum C-23-C-29) are found to be abundant in the insects (31-781 mu g/dry g), with a carbon preference index (CPI) of 5.1-31.5 and an average chain length (ACL) of 24.9-29.3. The isotopic compositions (mean +/- 1 sigma, n = 33) of the n-alkanes are -195 +/- 16 parts per thousand for hydrogen and -30.6 +/- 2.4 parts per thousand for carbon. The insect n-alkanes are depleted in D by approximately 30-40 parts per thousand compared with wax n-alkanes from C-3 (-155 +/- 25 parts per thousand) and C4 vascular plants (-167 +/- 13 parts per thousand), whereas their delta C-13 values fall between those of C-3 (-36.2 +/- 2.4 parts per thousand) and C4 plants (-20.3 +/- 2.4 parts per thousand). Thus, the contribution of insect-derived n-alkanes to soil and sediment could potentially shift dD records of n-alkanes toward more negative values and potentially muddle the assumed original C-3/C-4 balance in the delta C-13 records of the soil and sedimentary n-alkanes. n-Alkenes are also found in three insects (swallowtail, wasp and hornet). They are more depleted in D relative to the same carbon numbered n-alkanes (dD(n-alkene) - delta Dn-alkane = -17 +/- 16 parts per thousand), but the delta C-13 values are almost identical to those of the n-alkanes (delta C-13(n-alkene) +/- delta C-13(n-alkane) = 0.1 +/- 0.2 parts per thousand). These results suggest that these n-alkenes are desaturated products of the same carbon numbered n-alkanes. (C) 2012 Elsevier Ltd. All rights reserved.
  • Yaeko Suzuki, Yoshito Chikaraishi, Keita Yamada, Naohiro Yoshida
    BUNSEKI KAGAKU 61 9 805 - 810 2012年09月 [査読有り][通常論文]
     
    The elemental analyzer-isotope ratio mass spectrometer (EA-IRMS) has become increasingly important as a potential powerful tool for food authenticity. However, the lack of a reliable technique for the isotope ratio measurement, and limited availability of adequate international references are significantly regrettable, and should be improved immediately. Here we present results of an inter-laboratory test on the EA-IRMS determination of stable carbon, nitrogen and oxygen isotopic compositions (delta C-13, delta N-15 and delta O-18) in organic compounds. Three organic compounds (L-alanine for delta C-13 and delta N-15, and 1,2,3,4,6-penta-O-acetyl-alpha-D-glucopyranose and Dimethyl aminoterephthalate for delta O-18) were distributed and analyzed by a total of 25 laboratories. The results show that the 1 sigma standard deviation among laboratories is -11.9 +/- 0.2 parts per thousand (for delta C-13), -2.6 +/- 0.3 parts per thousand (for delta N-15), +32.3 +/- 1.0 parts per thousand (for delta O-18 of the glucopyranose derivative), and +25.9 +/- 2.3 parts per thousand (for delta O-18 of Dimethyl aminoterephthalate). Although the variations of the standard deviations for delta C-13, delta N-15 and delta O-18 (glucopyranose derivative) among laboratories are not so large compared to the instrument uncertainties, delta O-18 of Dimethyl aminoterephthalate, which contains nitrogen, shows a large variation among laboratories. This may have been caused by much contamination of N-2 to the CO peak on the EA-IRMS chromatogram, and may be improved by using a longer GC column (1.0 similar to 1.5 m) for chromatographic separation.
  • Taro Maeda, Euichi Hirose, Yoshito Chikaraishi, Masaru Kawato, Kiyotaka Takishita, Takao Yoshida, Heroen Verbruggen, Jiro Tanaka, Shigeru Shimamura, Yoshihiro Takaki, Masashi Tsuchiya, Kenji Iwai, Tadashi Maruyama
    PLOS ONE 7 7 2012年07月 [査読有り][通常論文]
     
    The sea slug Plakobranchus ocellatus (Sacoglossa, Gastropoda) retains photosynthetically active chloroplasts from ingested algae (functional kleptoplasts) in the epithelial cells of its digestive gland for up to 10 months. While its feeding behavior has not been observed in natural habitats, two hypotheses have been proposed: 1) adult P. ocellatus uses kleptoplasts to obtain photosynthates and nutritionally behaves as a photoautotroph without replenishing the kleptoplasts; or 2) it behaves as a mixotroph (photoautotroph and herbivorous consumer) and replenishes kleptoplasts continually or periodically. To address the question of which hypothesis is more likely, we examined the source algae for kleptoplasts and temporal changes in kleptoplast composition and nutritional contribution. By characterizing the temporal diversity of P. ocellatus kleptoplasts using rbcL sequences, we found that P. ocellatus harvests kleptoplasts from at least 8 different siphonous green algal species, that kleptoplasts from more than one species are present in each individual sea slug, and that the kleptoplast composition differs temporally. These results suggest that wild P. ocellatus often feed on multiple species of siphonous algae from which they continually obtain fresh chloroplasts. By estimating the trophic position of wild and starved P. ocellatus using the stable nitrogen isotopic composition of amino acids, we showed that despite the abundance of kleptoplasts, their photosynthates do not contribute greatly to the nutrition of wild P. ocellatus, but that kleptoplast photosynthates form a significant source of nutrition for starved sea slugs. The herbivorous nature of wild P. ocellatus is consistent with insights from molecular analyses indicating that kleptoplasts are frequently replenished from ingested algae, leading to the conclusion that natural populations of P. ocellatus do not rely on photosynthesis but mainly on the digestion of ingested algae.
  • 大河内 直彦, 力石 嘉人, 小川 奈々子
    化学と生物 50 6 430 - 434 日本農芸化学会 2012年06月01日 [査読無し][通常論文]
     
    生体中に含まれるアミノ酸の窒素安定同位体比を精密に測定することによって,自然界に暮らす生き物の栄養段階を推定する方法が開発された.この手法を用いれば,各種生態系の解析に役立つだけでなく,環境変化が生物の食性に及ぼしてきた影響や,過去の人類の食性など,さまざまな応用研究が可能になる.
  • Kiyotaka Takishita, Yoshito Chikaraishi, Michelle M. Leger, Eunsoo Kim, Akinori Yabuki, Naohiko Ohkouchi, Andrew J. Roger
    BIOLOGY DIRECT 7 2012年02月 [査読有り][通常論文]
     
    Sterols are key components of eukaryotic cellular membranes that are synthesized by multi-enzyme pathways that require molecular oxygen. Because prokaryotes fundamentally lack sterols, it is unclear how the vast diversity of bacterivorous eukaryotes that inhabit hypoxic environments obtain, or synthesize, sterols. Here we show that tetrahymanol, a triterpenoid that does not require molecular oxygen for its biosynthesis, likely functions as a surrogate of sterol in eukaryotes inhabiting oxygen-poor environments. Genes encoding the tetrahymanol synthesizing enzyme squalene-tetrahymanol cyclase were found from several phylogenetically diverged eukaryotes that live in oxygen-poor environments and appear to have been laterally transferred among such eukaryotes.
  • 高野 淑識, 力石 嘉人, 大河内 直彦
    地球化学 46 2 113 - 128 日本地球化学会 2012年 
    Since the first classification by Woese and Fox (1977), Archaea, one of three domains of life, had been originally believed to exist in extreme environments including high temperature, high salinity, low oxygen concentration. However, recent advances in molecular and phylogenic approaches revealed their widespread distribution in marine and terrestrial environment including deep subsurface biosphere. The planktonic and benthic archaeal assemblages include two major phyla Euryarchaeota and Crenarchaeota. The novel phylum have been also proposed recently as Thaumarchaota, Korarchaota, and Nanoarchaeota. To elucidate unknown archaeal ecology, we evaluated intra-molecular isotopic composition to focus into archaeal membrane lipid biosynthesis using 13C-tracing techniques. The novel molecular diagnosis showed heterogenous 13C-incorporation driven by salvage (recycling) and de novo pathways in energy-limited environment such as deep-sea environments. Here, we reviewed the recent knowledge of prokaryotic ecology and biogeochemistry from intra-molecular isotopic signatures.
  • Does the symbiotic scale-worm feed on the host mussel in deep-sea vent fields? Researches in Organic Geochemistry
    Takahashi, Y, Y. Sasaki, Y. Chikaraishi, M. Tsuchiya, H. Watanabe, T. Asahida, T. Maruyama, K. Fujikura
    Researches in Organic Geochemistry 28 23 - 26 2012年 [査読有り][通常論文]
  • Dirk Sachse, Isabelle Billault, Gabriel J. Bowen, Yoshito Chikaraishi, Todd E. Dawson, Sarah J. Feakins, Katherine H. Freeman, Clayton R. Magill, Francesca A. McInerney, Marcel T. J. van der Meer, Pratigya Polissar, Richard J. Robins, Julian P. Sachs, Hanns-Ludwig Schmidt, Alex L. Sessions, James W. C. White, Jason B. West, Ansgar Kahmen
    ANNUAL REVIEW OF EARTH AND PLANETARY SCIENCES, VOL 40 40 221 - 249 2012年 [査読有り][通常論文]
     
    Hydrogen-isotopic abundances of lipid biomarkers are emerging as important proxies in the study of ancient environments and ecosystems. A decade ago, pioneering studies made use of new analytical methods and demonstrated that the hydrogen-isotopic composition of individual lipids from aquatic and terrestrial organisms can be related to the composition of their growth (i.e., environmental) water. Subsequently, compound-specific deuterium/hydrogen (D/H) ratios of sedimentary biomarkers have been increasingly used as paleohydrological proxies over a range of geological timescales. Isotopic fractionation observed between hydrogen in environmental water and hydrogen in lipids, however, is sensitive to biochemical, physiological, and environmental influences on the composition of hydrogen available for biosynthesis in cells. Here we review the factors and processes that are known to influence the hydrogen-isotopic compositions of lipids-especially n-alkanes-from photosynthesizing organisms, and we provide a framework for interpreting their D/H ratios from ancient sediments and identify future research opportunities.
  • Maggie S. Strable, Carolyn L. Tschanz, Behzad Varamini, Yoshito Chikaraishi, Naohiko Ohkouchi, J. Thomas Brenna
    RAPID COMMUNICATIONS IN MASS SPECTROMETRY 25 23 3555 - 3562 2011年12月 [査読有り][通常論文]
     
    We report the first high-precision characterization of molecular and intramolecular delta N-15 of nucleosides derived from mammalian DNA. The influence of dietary protein level on brain amino acids and deoxyribonucleosides was determined to investigate whether high protein turnover would alter amino acid (15) N or (13) C values. Pregnant guinea pig dams were fed control diets, or high or low levels of dietary protein throughout gestation, and all pups were fed control diets. The cerebellar DNA of offspring was extracted at 2 and 120 days of life, nucleosides isolated and delta N-15 and delta C-13 values characterized. Mean diet delta N-15 was 0.45 +/- 0.33 parts per thousand, compared with cerebellar whole tissue and DNA delta N-15 = +4.1 +/- 0.7 parts per thousand and -4.5 +/- 0.4 parts per thousand, respectively. Cerebellar deoxythymidine (dT), deoxycytidine (dC), deoxyadenosine (dA), and deoxyguanosine (dG) delta N-15 were +1.4 +/- 0.4, -2.1 +/- 0.9, -7.2 +/- 0.3, and -10.4 +/- 0.5 parts per thousand, respectively. There were no changes in amino acid or deoxyribonucleoside delta N-15 values due to dietary protein level. Using known metabolic relationships, we developed equations to calculate the intramolecular delta N-15 values originating from aspartate (asp) in purines (pur) or pyrimidines (pyr), glutamine (glu), and glycine (gly) to be delta N-15(ASP-PUR), delta N-15(ASP-PYR), delta N-15(GLN), and delta N-15(GLY) +11.9 +/- 2.3 parts per thousand, +/- 7.0 +/- 2.0 parts per thousand, -9.1 +/- 2.4 parts per thousand, and -31.8 +/- 8.9 parts per thousand, respectively. A subset of twelve amino acids from food and brain had mean delta N-15 values of 4.3 +/- 3.2 parts per thousand and 13.8 +/- 3.1 parts per thousand, respectively, and delta N-15 values for gly and asp were 12.6 +/- 2.2 parts per thousand and 15.2 +/- 0.8 parts per thousand, respectively. A separate isotope tracer study detected no significant turnover of cerebellar DNA in the first six months of life. The large negative delta N-15 difference between gly and cerebellar purine N at the gly (7) position implies either that there is a major isotope effect during DNA synthesis, or that in utero gly has a different isotope ratio during rapid growth and metabolism from that in adult life. Our data show that cerebellar nucleoside intramolecular delta N-15 values vary over more than 40 parts per thousand and are not influenced by dietary protein level or age. Copyright (C) 2011 John Wiley & Sons, Ltd.
  • 力石 嘉人, 高野 淑識, 小川 奈々子, 佐々木 瑶子, 土屋 正史, 大河内 直彦
    Researches in organic geochemistry 27 3 - 11 日本有機地球化学会 2011年09月30日 [査読無し][通常論文]
     
    Recent evidences have suggested that compound-specific stable isotope analysis (CSIA) of amino acids has been employed as a new powerful method with that enables the estimation of trophic level of organisms in not only aquatic but also terrestrial food webs. This CSIA approach is based on contrasting the ^<15>N-enrichment with each trophic level between two common amino acids: glutamic acid shows significant enrichment of +8.0‰ with each trophic level, whereas phenylalanine shows little enrichment of +0.4‰. These ^<15>N-enrichments are well consistent in both aquatic and terrestrial organis...
  • Yoshito Chikaraishi, Nanako O. Ogawa, Hideyuki Doi, Naohiko Ohkouchi
    ECOLOGICAL RESEARCH 26 4 835 - 844 2011年07月 [査読有り][通常論文]
     
    Compound-specific stable isotope analysis (CSIA) of amino acids is a new method that enables estimates of trophic position for consumers in food webs. We examined the nitrogen isotopic composition (delta N-15) of amino acids of Japanese social insects (three bee, three wasp, and four hornet species) to evaluate the potential of CSIA of amino acids in studies of terrestrial food webs. For wasps, we also examined samples at different growth stages (ranging from egg to adult) to assess the effect of metamorphosis on CSIA estimates of trophic position. The delta N-15 values of bulk tissues for Japanese social insects are only weakly correlated with the biologically expected trophic positions. In contrast, the trophic positions estimated from the delta N-15 values of amino acids (yielding values of between 2.0 and 2.3 for bees, between 2.8 and 3.3 for wasps, and between 3.5 and 4.1 for hornets) are consistent with the biologically expected trophic positions for these insects (i.e., 2.0 for bees, 3.0 for wasps, and 3.0-4.0 for hornets). Although large variability is observed among the delta N-15 values of individual amino acids (e. g., ranging from 3.0 to 14.9 parts per thousand for phenylalanine), no significant change is observed in the trophic position during wasp metamorphosis. Thus, the CSIA of amino acids is a powerful tool for investigating not only aquatic food webs but also terrestrial food webs with predatory insects.
  • 宮地俊作, 馬谷原武之, 對馬孝治, 笹田勝寛, 河野英一, 伊藤絹子, 川端淳, 力石嘉人, 小川奈々子, 大河内直彦
    日本水産学会大会講演要旨集 2011 77  2011年03月27日 [査読無し][通常論文]
  • Youping Zhou, Kliti Grice, Yoshito Chikaraishi, Hilary Stuart-Williams, Graham D. Farquhar, Naohiko Ohkouchi
    PHYTOCHEMISTRY 72 2-3 207 - 213 2011年02月 [査読有り][通常論文]
     
    The hydrogen isotopic ratios (H-2/H-1) of land plant leaf water and the carbon-bound hydrogen of leaf wax lipids are valuable indicators for climatic, physiological, metabolic and geochemical studies. Temperature will exert a profound effect on the stable isotopic composition of leaf water and leaf lipids as it directly influences the isotopic equilibrium (IE) during leaf water evaporation and cellular water dissociation. It is also expected to affect the kinetics of enzymes involved in lipid biosynthesis, and therefore the balance of hydrogen inputs along different biochemical routes. We conducted a controlled growth experiment to examine the effect of temperature on the stable hydrogen isotopic composition of leaf water and the biological and biochemical isotopic fractionations during lipid biosynthesis. We find, that leaf water H-2 enrichment at 20 degrees C is lower than that at 30 degrees C. This is contrary to the expectation that at lower temperatures leaf water should be more enriched in H-2 due to a larger equilibrium isotope effect associated with evapotranspiration from the leaf if all other variables are held constant. A hypothesis is presented to explain the apparent discrepancy whereby lower temperature-induced down-regulation of available aquaporin water channels and/or partial closure of transmembrane water channel forces water flow to "detour" to a more convoluted apoplastic pathway, effectively increasing the length over which diffusion acts against advection as described by the Peclet effect (Farquhar and Lloyd, 1993) and decreasing the average leaf water enrichment. The impact of temperature on leaf water enrichment is not reflected in the biological isotopic fractionation or the biochemical isotopic fractionation during lipid biosynthesis. Neither the biological nor biochemical fractionations at 20 degrees C are significantly different from that at 30 degrees C, implying that temperature has a negligible effect on the isotopic fractionation during lipid biosynthesis. (C) 2010 Elsevier Ltd. All rights reserved.
  • 小川 奈々子, 力石 嘉人, 和田 英太郎, 大河内 直彦
    日本地球化学会年会要旨集 58 91 - 91 日本地球化学会 2011年 
    生物を構成する有機物の安定同位体比は、生態系における一次生産者の光合成メカニズムや基質、食物連鎖の構造や変化などを解析する上で、優れた指標である。生物を構成するアミノ酸では、捕食による窒素代謝の過程で、アミノ酸の種類により15N濃縮の大きさに差が生じることが明らかとなってきた。この結果はほとんどの水界生態系・陸上生態系生物に共通しており、こうしたアミノ酸窒素安定同位体比の比較から、生態系生物の栄養段階の算出も可能となる。本講演ではバイカル湖での結果を中心に、私たちの研究グループにおけるアミノ酸の分子レベル窒素安定同位体比を用いた生態系生物に関する研究について紹介する。
  • 内藤 裕一, Honch Noah, 力石 嘉人, 大河内 直彦, 米田 穣
    日本地球化学会年会要旨集 58 0 151 - 151 一般社団法人日本地球化学会 2011年 [査読有り][通常論文]
     
    先史日本人の食性を復元するために、様々な遺跡から出土した人骨・動物遺存体試料についてアミノ酸の窒素同位体分析を試みた。分析の結果、地域や時代によって特徴的な骨試料の窒素同位体比パターンがみられ、それは特にグルタミン酸(沿岸部で+23~+32‰、内陸部で+10~+12‰)とフェニルアラニン(沿岸部で0~+7‰、内陸部で+6~+7‰)の同位体比において顕著であった。ヒトの食料に対する海洋・淡水・陸上生態系からのタンパク質の寄与率評価に、フェニルアラニンの窒素同位体比が有用であることは特筆すべきである。例えば、沿岸部の縄文人集団はおよそ70%以上のタンパク質を海産物に依存していたこと、反対に内陸部や旧石器時代の集団では陸上資源以外はほとんど利用していなかったこと等が明らかとなった。
  • Methyl and ethyl chloroformate derivatizations for compound-specific stable isotope analysis (CSIA) of fatty acids
    Akiko S. Goto, Takashi Korenaga, Yoshito Chikaraishi
    Researches in Organic Geochemistry 27 91 - 95 2011年 [査読有り][通常論文]
  • Yuichi I. Naito, Noah V. Honch, Yoshito Chikaraishi, Naohiko Ohkouchi, Minoru Yoneda
    AMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY 144 223 - 223 2011年 [査読有り][通常論文]
  • Akamatsu F, Yamamoto M, Chikaraishi Y, Toda H
    Researches in Organic Geochemistry 26 107 - 114 日本有機地球化学会 2010年12月 [査読有り][通常論文]
  • Yoshinori Takano, Yoshito Chikaraishi, Nanako O. Ogawa, Hidetaka Nomaki, Yuki Morono, Fumio Inagaki, Hiroshi Kitazato, Kai-Uwe Hinrichs, Naohiko Ohkouchi
    NATURE GEOSCIENCE 3 12 858 - 861 2010年12月 [査読有り][通常論文]
     
    Deep-sea sediments harbour a vast biosphere. Archaea-one of the three domains of life(1)-are prevalent in marine environments(2-5), and comprise a significant fraction of the biomass in marine sediments(6). Archaeal membranes are well characterized, and are comprised of a glycerol backbone and a nonpolar isoprenoid chain. However, the ecology of sedimentary archaea remains elusive, because it is difficult to grow them in the laboratory. Here, we trace the fate of C-13-labelled glucose added to marine sediments in Sagami Bay, Japan, to determine the in situ mechanisms of membrane synthesis. Following the addition of labelled glucose to sediment samples collected in the region, we placed the cores on the sea floor and sampled them after 9 and 405 days. We found that the C-13 was incorporated into the glycerol backbone of archaeal membranes; C-13 was apparent after 9 days of incubation, but most pronounced after 405 days. However, the isoprenoid chain of the membranes remained unlabelled. On the basis of the differential uptake of C-13, we suggest that the glycerol unit is synthesized de novo, whereas the isoprenoid unit is synthesized from relic archaeal membranes and detritus, because of the prevalence of these compounds in marine sediments. We therefore suggest that some benthic archaea build their membranes by recycling sedimentary organic compounds.
  • Yuichi I. Naito, Noah V. Honch, Yoshito Chikaraishi, Naohiko Ohkouchi, Minoru Yoneda
    AMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY 143 1 31 - 40 2010年09月 [査読有り][通常論文]
     
    Nitrogen stable isotopes analysis of individual bone collagen amino acids was applied to archeological samples as a new tool for assessing the composition of ancient human diets and calibrating radiocarbon dates. We used this technique to investigate human and faunal samples from the Kitakogane shell midden in Hokkaido, Japan (5,300-6,000 cal BP). Using compound-specific nitrogen isotope analysis of individual amino acids, we aimed to estimate i) the quantitative contribution of marine and terrestrial protein to the human diet, and ii) the mean trophic level (TL) from which dietary protein was derived from marine ecosystems. Data were interpreted with reference to the amino acid trophic level (TLAA) model, which uses empirical amino acid delta N-15 from modern marine fauna to construct mathematical equations that predict the trophic position of organisms. The TLAA model produced realistic TL estimates for the Kitakogane marine animals. However, this model was not appropriate for the interpretation of human amino acid delta N-15, as dietary protein is derived from both marine and terrestrial environments. Hence, we developed a series of relevant equations that considered the consumption of dietary resources from both ecosystems. Using these equations, the mean percentage of marine protein in the Kitakogane human diet was estimated to be 74%. Although this study is one of the first systematic investigations of amino acid delta N-15 in archeological bone collagen, we believe that this technique is extremely useful for TL reconstruction, palaeodietary interpretation, and the correction of marine reservoir effects for radiocarbon dating. Am J Phys Anthropol 143:31-40, 2010. (C) 2010 Wiley-Liss, Inc.
  • Yoshinori Takano, Yuichiro Kashiyama, Nanako O. Ogawa, Yoshito Chikaraishi, Naohiko Ohkouchi
    RAPID COMMUNICATIONS IN MASS SPECTROMETRY 24 16 2317 - 2323 2010年08月 [査読有り][通常論文]
     
    We have established a procedure for removing interfering materials from extracts of geological and biological samples, in order to determine precise compound-specific nitrogen isotopic compositions of amino acids. We employed cation-exchange chromatography of protein and non-protein amino acids prior to derivatization for gas chromatographic separation. The average recovery of a standard amino acid solution was better than 94%, without nitrogen isotope fractionation during the cation-exchange chromatography. We applied the procedure to various environmental samples including 'hard' (calcareous, siliceous, rock and sediment samples) and 'soft' materials (aggregated microbial samples and biological soft tissue samples). We conclude that cation-exchange chromatography is a pre-treatment procedure which should be widely useful for the determination of compound-specific nitrogen isotopic compositions of amino acids. Copyright (C) 2010 John Wiley & Sons, Ltd.
  • 内藤祐一, 山口保彦, 力石嘉人, 大河内直彦
    Researches in Organic Geochemistry 26 139 - 145 日本有機地球化学会 2010年 [査読有り][通常論文]
  • Yuichi I. Naito, Yoshito Chikaraishi, Naohiko Ohkouchi, Hitoshi Mukai, Yasuyuki Shibata, Noah V. Honch, Yukio Dodo, Hajime Ishida, Tetsuya Amano, Hiroko Ono, Minoru Yoneda
    RADIOCARBON 52 2 671 - 681 2010年 [査読有り][通常論文]
     
    The relative contribution of marine-derived carbon in the ancient diet is essential for correcting the marine reservoir effect on the radiocarbon age of archaeological human remains. In this study, we evaluated the marine protein consumption of 3 human populations from the Okhotsk culture (about AD 550-1200) in Hokkaido, Japan, based on stable carbon and nitrogen isotopic compositions in bulk bone collagen as well as the nitrogen isotopic composition of glutamic acid and phenylalanine. Despite the similarity of carbon and nitrogen isotopic composition of bulk collagens, nitrogen isotopic composition of their constituent amino acids suggests differences in fur seal contributions among northern Hokkaido (0-24% for Kafukai 1, 0-10% for Hamanaka 2) and eastern Hokkaido (78-80% for Moyoro) populations. It suggests that nitrogen composition of glutamic acid and phenylalanine could provide a detailed picture of ancient human subsistence.
  • Yoshito Chikaraishi, Nanako O. Ogawa, Yuichiro Kashiyama, Yoshinori Takano, Hisami Suga, Akiko Tomitani, Hideaki Miyashita, Hiroshi Kitazato, Naohiko Ohkouchi
    LIMNOLOGY AND OCEANOGRAPHY-METHODS 7 740 - 750 2009年11月 [査読有り][通常論文]
     
    The nitrogen isotopic composition (delta N-15) of amino acids is potentially useful as an alternative method for estimating the trophic levels of organisms in food webs. However, because this "amino acid method" has been constructed from the observations of only a few case studies of food-consumer combinations in previous studies, the universality of the approach remains unclear. In this study, we investigated the delta N-15 signatures of amino acids in 17 photoautotrophs and the trophic relationships during four controlled feeding experiments using green algae, zooplankton, and fish. The results are consistent with those reported in previous studies, implying that the amino acid method can be applied to a variety of organisms. From these and previously published data, we estimate the two factors (beta, isotope differences among amino acids in primary producers; Delta the N-15-enrichment factor for each trophic level) required to calculate the trophic level. Based on the lowest error (1 sigma = 0.12) in the estimated trophic level, we conclude that a comparison of the delta N-15 values for glutamic acid and phenylalanine is most useful in calculating precise estimates of the trophic level, using the following equation: trophic level (TLGlu/Phe) = (delta N-15(Glu) - delta N-15(Phe) -3.4)/7.6 + 1.
  • Hidetaka Nomaki, Naohiko Ohkouchi, Petra Heinz, Hisami Suga, Yoshito Chikaraishi, Nanako O. Ogawa, Kouhei Matsumoto, Hiroshi Kitazato
    DEEP-SEA RESEARCH PART I-OCEANOGRAPHIC RESEARCH PAPERS 56 9 1488 - 1503 2009年09月 [査読有り][通常論文]
     
    We conducted an in situ feeding experiment using C-13-labeled unicellular algae in Sagami Bay, Japan (water depth, 1450 m), in order to understand the fate of lipid compounds in phytodetritus at the deep-sea floor. We examined the incorporation of excess C-13 into lipid compounds extracted from bulk sediments and benthic foraminiferall cells. C-13-enriched fatty acids derived from C-13-labeled algae were exponentially degraded during 6 days of incubation in the sediment. Subsequent enrichments in C-13 in sedimentary n-C-15, anteiso-C-17, and C-17 fatty acids indicated the microbial degradation of algal material and production of bacterial biomass in the sediment. We observed the incorporation of C-13-labeled algal phytol and fatty acids into foraminiferal cells. The compositions of C-13-labeled algal lipids in foraminiferal cells were different from those in the bulk sediments, indicating that foraminiferal feeding and digestion influenced the lipid distribution in the sediments. Furthermore, some sterols in Globobulimina affinis (e.g., 24-ethylcholesta-5,22-dien-3 beta-ol, 24-ethylcholest-5-en-3 beta-ol, and 23,24-dimethylcholesta-5,22E-dien-3 beta-ol) were newly produced via the modification of dietary algal sterols within 4-6 days. In addition to the effects of bacteria, feeding by benthic foraminifera can result in a significant reorganization of the composition of organic matter and influence benthic food webs and carbon cycling at the deep-sea floor. (C) 2009 Elsevier Ltd. All rights reserved.
  • Yoshito Chikaraishi, Ryouichi Tanaka, Ayumi Tanaka, Naohiko Ohkouchi
    ORGANIC GEOCHEMISTRY 40 5 569 - 573 2009年05月 [査読有り][通常論文]
     
    Deuterium (D) depletion in phytol relative to ambient water as well as other lipids has been widely observed in various biological and geological samples; however, the mechanism for the depletion remains unknown. We have determined the hydrogen isotopic compositions of phytol and its precursors in cucumber cotyledons and have evaluated the fractionation of hydrogen isotopes during phytol biosynthesis. The hydrogen isotopic compositions of geranylgeraniol, dihydrogeranylgeraniol, tetrahydrogeranylgeraniol and phytol are -281 parts per thousand, -302 parts per thousand, -325 parts per thousand and -345 parts per thousand, respectively. The results suggest that significantly D-depleted hydrogen is incorporated stepwise during hydrogenation of geranylgeraniol to phytol. We conclude that hydrogenation is important in controlling D depletion in phytol. (C) 2009 Elsevier Ltd. All rights reserved.
  • 力石 嘉人
    日本地球化学会年会要旨集 56 155 - 155 日本地球化学会 2009年 
    これまで,有機化合物やその安定同位体比を用いた様々な指標が提案され,地球化学の様々な課題に対して多くの知見を提供している。近年,生理学的な基本原理をよく理解して,そのしくみを利用した新規指標の開発(または,従来の指標の大幅な改善)が行われるようになりつつある。生物は,体内の生理活性を非常に上手くコントロールし,その調整には様々な特性の有機化合物が密接に関係している。また生物による有機化合物の生合成・代謝は,ほとんどの場合,安定同位体組成の変化を伴い,その大きさは反応の進み具合と密接な関係を持つ。すなわち,我々が知りたい生物地球化学的情報にダイレクトに関わる生理活性を見出し,それに関係する有機化合物,または安定同位体比の変化を環境試料から明確にとらえることができれば,それが優れた指標となる可能性が高い。発表では、生理学的な知見を利用する新指標のアイデア・基本原理とその実例を紹介する。
  • 柏山 祐一郎, 力石 嘉人, 小川 奈々子, 大河内 直彦
    日本地球化学会年会要旨集 56 152 - 152 日本地球化学会 2009年 
    クロロフィルのテトラピロール骨格のメチン架橋位の炭素同位体組成を,分子全体と酸化分解により得られるマレイミド類の炭素同位体組成を比較することで求められる.本講演では,高等植物とシアノバクテリアから得られたクロロフィルaの値をもとに,後者のチン架橋位の炭素同位体組成がβカルボキシレーションによる重炭酸の同化を反映して,実際に大きな値をとるかどうかを検証する.また,東北日本の中新統女川層から得られた化石ポルフィリン(のメチン架橋位の炭素同位体組成を求め,当時の基礎生産におけるシアノバクテリアの寄与について議論する.
  • 山口保彦, 力石嘉人, 横山祐典, 大河内直彦
    Researches in Organic Geochemistry 25 71 - 83 2009年 [査読有り][通常論文]
  • Yoshinori Takano, Yoshito Chikaraishi, Nanako O. Ogawa, Hiroshi Kitazato, Naohiko Ohkouchi
    ANALYTICAL CHEMISTRY 81 1 394 - 399 2009年01月 [査読有り][通常論文]
     
    We have developed an analytical method to determine the compound-specific nitrogen isotope compositions of individual amino acid enantiomers using gas chromatography/combustion/isotope ratio mass spectrometry. A novel derivatization of amino acid diastereomers by optically active (R)-(-)-2-butanol or (S)-(+)-2-butanol offers two advantages for nitrogen isotope analysis. First, chromatographic chiral separation can be achieved without the use of chiral stationary-phase columns. Second, the elution order of these compounds on the chromatogram. can be switched by a designated esterification reaction. We applied the method to the compound-specific nitrogen isotope analysis of D- and L-alanine in a peptidoglycan derived from the cell walls of cultured bacteria (Firmicutes and Actinobacteria; Enterococcus laecalis, Staphylococcus aureus, Staphylococcus staphylolyticus, Lactobacillus acidophilus, Bacillus subtilis, Micrococcus luteus, and Streptomyces sp.), natural whole bacterial cells (Bacillus subtilis var. natto), (pseudo)-peptidoglycan from archaea (Methanobacterium sp.), and cell wall from eukaryota (Saccharomyces cerevisiae). We observed statistically significant differences in nitrogen isotopic compositions; e.g., delta N-15 (parts per thousand vs air) in Staphylococcus staphylolyticus for D-alanine (19.2 +/- 0.5 parts per thousand, n = 4) and L-alanine (21.3 +/- 0.8 parts per thousand, n = 4) and in Bacillus subtilis for D-alanine (6.2 +/- 0.2 parts per thousand, n = 3) and L-alanine (8.2 +/- 0.4 parts per thousand, n = 3). These results suggest that enzymatic reaction pathways, including the alanine racemase reaction, produce a nitrogen isotopic difference in amino acid enantiomers, resulting in N-15-depleted D-alanine. This method is expected to facilitate compound-specific nitrogen isotope studies of amino acid stereoisomers.
  • Y. Kashiyama, H. Miyashita, S. Ohkubo, N.O. Ogawa, Y. Chikaraishi, Y. Takano, H. Suga, T. Toyofuku, H. Nomaki, H. Kitazato, T. Nagata, N. Ohkouchi
    Science 321 5889 658 - 658 2008年08月01日 [査読有り][通常論文]
  • Yaeko Suzuki, Yoshito Chikaraishi, Nanako O. Ogawa, Naohiko Ohkouchi, Takashi Korenaga
    FOOD CHEMISTRY 109 2 470 - 475 2008年07月 [査読有り][通常論文]
     
    We determined carbon and nitrogen contents (C and N contents) and stable carbon, nitrogen, and oxygen isotopic compositions (delta C-13, delta N-15, and delta O-18) of polished rice in order to develop a simple method to discriminate its geographical origin. As a first attempt, we examined a single cultivar, Koshihikari rice, from 14 different cultivation areas including Australia (n = 1), Japan (n = 12), and USA (n = 1). For all rice samples, C and N contents and the isotopic compositions are consistent with those of general plant materials, being 37.2-40.0% (C content), 0.8-1.4% (N content), -27.1 to -25.4% (delta C-13), +0.4 to +9.0% (delta N-15), and +18.8 to +22.9% (delta O-18). However, its cultivated area is clearly distinguished by a pentagonal radar plot based on the elemental and isotopic compositions. Thus, the comparison of C and N contents and delta C-13, delta N-15, and delta O-18 values would potentially be useful for rapid and routine discrimination of geographical origin of the polished rice. (C) 2008 Elsevier Ltd. All rights reserved.
  • Rumiko Nakashita, Yaeko Suzuki, Fumikazu Akamatsu, Yoshiko Iizumi, Takashi Korenaga, Yoshito Chikaraishi
    ANALYTICA CHIMICA ACTA 617 1-2 148 - 152 2008年06月 [査読有り][通常論文]
     
    Stable isotope analysis of organic elements such as carbon and nitrogen has been employed as a powerful tool for provenance determination of food materials, because isotopic compositions of the materials reflect many factors in natural environment. In this study, we examined carbon, nitrogen, and oxygen isotope signatures of beef from Australia, Japan, and USA, in order to confirm the method as a potential tool for verifying geographical origin of beef commercially distributed in Japan. Defatted dry matter of beef from USA was characterized by higher carbon isotopic composition (-13.6%omicron to -11.1%omicron than that from Japan (-19.6%omicron to -17.0%omicron) and Australia (-23.6%omicron to -18.7%omicron). That from Australia was characterized by higher oxygen isotopic composition (+15.0%omicron to +19.4%omicron) than that from Japan (+7.3%omicron to +13.6%omicron) and USA (+9.5%omicron to +11.7%omicron). The oxygen isotopic composition in Japanese beef showed a positive correlation with the isotopic composition of cattle drinking water, the difference in which is clearly latitude dependent. These results suggest that a comparison of carbon, nitrogen, and oxygen isotopic compositions is applicable as a potential tool to discriminate the provenance of beef not only between different countries (i.e. Australia, Japan, and USA) but also among different regions within Japan. (C) 2008 Elsevier B.V. All rights reserved.
  • Robert Gwyn Jenkins, Yoshinori Hikida, Yoshito Chikaraishi, Naohiko Ohkouchi, Kazushige Tanabe
    ISLAND ARC 17 2 261 - 269 2008年06月 [査読有り][通常論文]
     
    Ooid-like coated grains are found in the Late Cretaceous methane-seep deposits in the Nakagawa area, Hokkaido, Japan. The coated grains were examined using macro- and microscopic observations, electron-probe microanalysis, and biomarker analysis. They are round- to oval-shaped, with nuclei consisting of fractured sediment and micritic envelopes. The fractures probably occurred as a result of increasing hydrostatic pressure when the sediment was still unconsolidated or weakly consolidated. Biomarker analysis revealed that two types of molecules, crocetane and PMI, are predominant in the hydrocarbon fraction with highly negative carbon isotopic composition as low as -122 parts per thousand (vs Vienna Peedee Belemnite). These data suggest that the coated grains were formed under the influence of anaerobic oxidation of methane, near the sediment/seawater interface. The presence of such grains indicates that methane-containing pore water reached the sea floor at that time.
  • 高野 淑識, 野牧 秀隆, 小川 奈々子, 力石 嘉人, 稲垣 史生, 北里 洋, 大河内 直彦
    日本地球化学会年会要旨集 55 154 - 154 日本地球化学会 2008年 
    原核生物の古細菌や真正細菌には、特有のバイオマーカーが存在する。例えば古細菌は、カルドアーキオール(Caldarchaeol)やクレンアーキオール(Crenarchaeol)に代表される極性脂質化合物を保有する。それらの分子は、微生物の成育・増殖とともに新たに産生されるため、同位体トレーサー基質を取り込んだ場合、その代謝のシグナルは、微生物細胞やそれを構成するバイオマーカー分子に反映される。堆積物から古細菌の細胞のみを単離するのは困難なため、古細菌を構成するバイオマーカー分子を分離・解析することで炭素源の取込みや代謝の活性を評価できる(eg. Pearson et al., 2001)。まず、海底堆積物中での微生物活性を測る目的で、古細菌に由来するバイオマーカーを単離・精製し、分子レベル安定炭素同位体比を評価する分析ラインを確立した。次に、海底表層と堆積物浅層で同位体ラベルを使ったトレーサー実験試料を用いて、海底堆積物に棲む古細菌の代謝活性の有無を調べた。海底堆積物浅層に棲息する古細菌は、1) 埋没後も脂質の生合成が行われ代謝活性があること、2)迫{9日間という時間スケールであっても代謝活性のシグナルが観測されることを示した。
  • 小川 奈々子, 力石 嘉人, 柏山 祐一郎, 富谷 朗子, 北里 洋, 大河内 直彦
    日本地球化学会年会要旨集 55 184 - 184 日本地球化学会 2008年 
    光合成生物は、光(エネルギー)の吸収(捕集)のために、光合成色素とよばれる有色の化合物を用いている。それらは大きくクロロフィル、カロテノイド、フィコビリンの三つに分類される。このうちクロロフィルとカロチノイドは高等植物や多くの藻類に存在するが、フィコビリンはシアノバクテリアや、紅藻などの藻類の一部がもつ色素である。シアノバクテリアは、これまでのクロロフィル系の色素化合物とその関連有機化合物の安定同位体比研究から、先カンブリア代や海洋無酸素事変時の地球環境の変動に大きく関与していることが示唆されてきた。一方、フィコビリンはシアノバクテリアがもつ光合成色素であり、シアノバクテリアのバイオマーカーとして各種情報を保持している可能性が推察されるものの、蛋白質と結合しているため従来の実験手法では分離測定が困難であった。したがって、これまで地球化学的な知見をあまり多く得ることができていない。本研究では、1)フィコビリンの分析法の確立と、2)それが記録する地球生物学的な情報を知るために、迫{シアノバクテリア試料中に含まれる「フィコビリン蛋白質(phycobiliproteins, PBP)」を分離し、その安定同位体比を測定した。実験には室温で迫{された各種のシアノバクテリアを用いた。リン酸バッファーを用いて抽出したPBPは、逆相HPLCにより分離した(図1)。各PBPはピーク毎にフラクションコレクターによって捕集し、安定同位体比等の分析を行った。本講演では、その結果について報告する。
  • 高野 淑識, 力石 嘉人, 小川 奈々子, 北里 洋, 大河内 直彦
    日本地球化学会年会要旨集 55 189 - 189 日本地球化学会 2008年 
    原核生物のうち真正細菌の細胞壁には、主としてその強度と形態を支えるために堅い層が存在する。特にグラム陽性の細胞壁は、その約90%がペプチドグリカン(数層~約25層)から構成され、凖難分解性の性質を持つ。細胞内のタンパク質を構成するアミノ酸は、基本的にL-体であるが、細胞壁のペプチドグリカンには、2つの糖誘導体であるN-アセチルグルコサミンとN-アセチルムラミン酸にD-アラニンやD-グルタミン酸などのD-アミノ酸を含むペプチドが架橋している。ペプチドグリカン由来のD-アラニンは、真正細菌のバイオマーカーの一つと考えられている。ここでは、まず様々な地球化学試料に含まれる立体異性体分子レベル窒素同位体比を得るための分析法を確立した。次に、応用の一つとして原核生物の細胞組織であるペプチドグリカン、シュードペプチドグリカン由来のD-, L-アラニンについて評価し、立体異性体分子レベルで特徴的な同位体比の分配が見られたので報告する。
  • 力石 嘉人, 小川 奈々子, 柏山 祐一郎, 高野 淑識, 北里 洋, 大河内 直彦
    日本地球化学会年会要旨集 55 187 - 187 日本地球化学会 2008年 
    生体試料のバルクの窒素安定同位体比は、食物連鎖網の解析や栄養段階の推定などの生態学研究において、ほとんど必須のツールとして広く用いられている。しかし、食物連鎖に伴う窒素同位体比の上昇が生物ごとに大きく変動することや、一次生産者の妥当な同位体比を得ることが難しいことから、見積もられる栄養段階の誤差が常に議論の対象になってきた。ところが近年、生物に含まれるアミノ酸には、食物連鎖に伴い15Nが濃縮するものと、食物連鎖の影響を受けずに同位体比が変化しないものが存在し、両者の同位体比を比較することで、その生物の栄養段階や、食物連鎖網のベースにある生物の同位体比を精度良く見積もることができることがわかってきた。発表では、アミノ酸の窒素同位体比分析法の概要と、これまでに我々の研究室で得られた結果を紹介する。
  • 内藤 裕一, Noah V. Honch, 大河内 直彦, 小川 奈々子, 力石 嘉人, 高野 淑識, 柏山 祐一郎, 米田 穣
    日本地球化学会年会要旨集 55 0 188 - 188 一般社団法人日本地球化学会 2008年 [査読有り][通常論文]
     
    生体試料におけるアミノ酸の窒素同位体比分析は、海洋・湖沼生態系の構造解析法として有効性が提唱されている。しかし、陸環境や古生態系に対する同手法の有効性はまだ検討が始まったばかりである。遺跡から出土する骨試料に残存する生体タンパク質(コラーゲン)は化学的に安定で変性作用を受けにくいため、過去の生態系構造を解析する好材料となる可能性がある。本研究では、陸・海双方の食料資源を利用した北海道の縄文人骨と彼らの残した動物骨を主な分析対象として、ヒトを含めた当時の生態系構造の解析にアミノ酸窒素同位体分析を応用し、その有効性を検討した。さらに特定のアミノ酸の窒素同位体比から人々の食習慣について定量的な復元を試みた。
  • 力石 嘉人, 大場 康弘
    Researches in Organic Geochemistry 23/24 99 - 122 日本有機地球化学会 2008年 [査読有り][通常論文]
     
    One of the most powerful techniques in the molecular isotope studies is compound-specific isotope analysis (CSIA) by gas chromatograph/isotope ratio mass spectrometer (GC/IRMS), which allows a rapid and precise determination of stable carbon, nitrogen, and hydrogen (and oxygen) isotopic compositions of individual compounds even in complex mixture of components. After commercial production of GC/IRMS in the 1990s, CSIA has explosively been used for many fields of studies, particularly among the organic geochemical community as a powerful tool for tracing sources and delivery of organic compounds in geological and geographical samples and for reconstructing paleoenvironments. However, it is also true that fundamental analytical parameters of GC/IRMS has not been known extensively, which often leads to unreliable determination of the isotopic compositions. Unfortunately, based on such unreliable determination, several studies have unconsciously reported essentially inaccurate data and associated discussion. Therefore, in this paper, we review a brief outline of GC/IRMS and associated methodologies, and summarize the instrumental factors influencing accuracy and precision of the isotope measurements. We hope that this paper is useful for applying CSIA to future studies.
  • Yoshito Chikaraishi, Yuichiro Kashiyama, Nanako O. Ogawa, Hiroshi Kitazato, Mitsuru Satoh, Shinya Nomoto, Naohiko Ohkouchi
    ORGANIC GEOCHEMISTRY 39 5 510 - 520 2008年 [査読有り][通常論文]
     
    The stable nitrogen isotopic signature of natural tetrapyrroles such as chloro- and pheo-pigments and alkylporphyrins is a potentially valuable proxy for the reconstruction of the nitrogen cycle of modern aquatic environments and of the geological past. However, its application has been limited due to analytical difficulties. In this study, we developed a method to determine stable nitrogen isotopic composition of tetrapyrroles by a combination of chemical conversion into monopyrrole units (i.e. maleimides) and their isotope analysis by gas chromatography/combustion/isotope ratio mass spectrometry (GC/C/IRMS). Two authentic (pyropheophorbide a and mesoporphyrin IX methylester) and four natural (chlorophyll a, deoxophylloerythroetioporphyrin (DPEP), and two 17-nor-DPEP) tetrapyrroles were converted to maleimides by HCl treatment and chromic acid oxidation. The stable nitrogen isotopic composition of the maleimides can be determined by GC/C/IRMS, with a standard deviation (1 sigma) of better than +/- 0.5 parts per thousand and the minimum sample amount of 0.8 nmol N. The isotopic composition of the maleimides is consistent with that of the original tetrapyrroles, suggesting nitrogen isotopic fractionation during the chemical treatment was insignificant. Further, no substantial difference is observed in the isotopic composition among the maleimides derived from a single tetrapyrrole. The developed method is applicable for the nitrogen isotope analysis of natural tetrapyrroles in various biological and geological samples. (C) 2007 Elsevier Ltd. All rights reserved.
  • Naohiko Ohkouchi, Yoji Nakajima, Nanako O. Ogawa, Yoshito Chikaraishi, Hisami Suga, Saburo Sakai, Hiroshi Kitazato
    ORGANIC GEOCHEMISTRY 39 5 521 - 531 2008年 [査読有り][通常論文]
     
    We report carbon isotopic compositions of tetrapyrrole nuclei (chlorophyllides) and side chains (phytol or farnesol) of chlorophyll a, bacteriochlorophyll a, and bacteriochlorophylls e isolated from several depths in the saline meromictic Lake Kaiike, Japan. The chlorophyllides are substantially enriched in C-13 relative to the side chains in all the depths of the lake, namely oxic mixolimnion, chemocline, anoxic monimolimnion, and benthic microbial mat. The isotopic compositions of chlorophyllide moieties are strongly related to those of the whole molecule (chloropigments; r(2) = 0.94) with the former being 1.8 +/- 0.8 parts per thousand (1 sigma, n = 18) enriched in C-13 relative to the latter. No significant difference was observed between chlorophyll species. The heterogeneity of C-13 in the chloropigments call be ascribed to differences between the biosynthetic pathways of chlorophyllides and side chains. The alkyl porphyrins in the geological samples are derived from the chlorophyllides, whose carbon skeleton is ultimately inherited from glutamate, one of the major amino acids ill the cell. Together with the isotopic relationship between chlorophylls and cell previously reported, we estimate that the carbon isotopic composition of DPEP, a major C-32 alkyl porphyrin in the geological samples, is similar to 1.8 parts per thousand enriched in C-13 relative to the cell. (C) 2007 Elsevier Ltd. All rights reserved.
  • N. Ohkouhi, T. I. Eglinton, M. Toyoda, Y. Chikaraishi, H. Tokuyama, H. Miura, Y. Yokoyama
    GEOCHIMICA ET COSMOCHIMICA ACTA 71 15 A732 - A732 2007年08月 [査読有り][通常論文]
  • Yoshito Chikaraishi, Hiroshi Naraoka
    ORGANIC GEOCHEMISTRY 38 2 198 - 215 2007年 [査読有り][通常論文]
     
    Carbon (delta C-13) and hydrogen (delta D) isotopic compositions of long-chain n-alkanoic acids, n-alkanes and n-alkanols from plant leaves including C3 angiosperm, C3 gymnosperm, C4 and CAM plants were determined in order to clarify detailed isotopic relationships among the three classes of n-alkyl compounds in terrestrial higher plants. For all plant species, the three classes of n-alkyl compounds have a similar range of delta C-13 and delta D values within a single species. However, most plants show a small but significant systematic difference in both delta C-13 and delta D values with respect to biosynthetically corresponding carbon-numbered compounds. In general, n-alkane and n-alkanol are enriched in C-13 (averaging 1.4 +/- 1.1 parts per thousand and 1.3 +/- 1.37 parts per thousand, respectively) but depleted in D (25 +/- 16 parts per thousand and 15 +/- 12 parts per thousand, respectively) relative to the corresponding carbon-numbered n-alkanoic acid. Moreover, the magnitude of the isotope difference is quite similar in all plants including different types of photosynthesis (C3, C4 and CAM). These results suggest that C-13- and D-discriminations occur at biosynthetic branching points during synthesis of n-alkanoic acid, n-alkane and n-alkanol from a common precursor, and that their fractionation mechanisms are common to all plant species. This systematic isotopic relationship between plant n-alkyl compounds will be useful to compare isotope records between different n-alkyl compounds in various geological samples. (c) 2006 Elsevier Ltd. All rights reserved.
  • Yoshito Chikaraishi, Kohei Matsumoto, Hiroshi Kitazato, Naohiko Ohkouchi
    ORGANIC GEOCHEMISTRY 38 6 985 - 1001 2007年 [査読有り][通常論文]
     
    Pheopigments such as pheophytin a, pyropheophytin a and steryl chlorin esters are abundant chlorophyll transformation products in many oceanic and lacustrine sedimentary environments. They have been widely used as direct indicators of phytoplankton and zooplankton activity in aquatic environments. In this study, we evaluate the sources and transformation processes of pheopigments in a sediment core from Lake Haruna (Japan), based on stable carbon (delta C-13) and hydrogen (delta D) isotopic composition of phytol and sterols as side chains of pheopigments. The isotopic compositions of phytol from sedimentary pheophytin a (delta C-13 = -29.2 parts per thousand to -27.6 parts per thousand, delta D = -388 parts per thousand to -376 parts per thousand) and some sterols from steryl chlorin esters (e.g. 24-methycholesta-5,22-dien-3 beta-ol; delta C-13 = -29.4 parts per thousand to -27.9 parts per thousand, delta D = -340 parts per thousand to -325 parts per thousand) are close to those of phytol (delta C-13 = -31.7 parts per thousand to -27.0 parts per thousand, delta D = -385 parts per thousand to -371 parts per thousand) and corresponding sterols (e.g. 24-methycholesta-5,22-dien-3 beta-ol; delta C-13 = -28.4 parts per thousand to -28.1 parts per thousand, delta D = -335 parts per thousand to -320 parts per thousand) from modern phytoplankton. The isotopic signatures are consistent with an origin exclusively from aquatic organisms. In contrast, the isotopic compositions of phytol from pyropheophytin a (delta C-13 = -31.7 parts per thousand to -29.1 parts per thousand, delta D = -379 parts per thousand to -341 parts per thousand) and other sterols from steryl chlorin esters (e.g. 24-ethyleholest-5-en-3 beta-ol, delta C-13 = -33.2 parts per thousand to -30.2 parts per thousand, delta D = -298 parts per thousand to -270 parts per thousand) vary throughout the core, with values ranging between those from modern phytoplankton (e.g. 24-ethylcholest-5-en-3 beta-ol; delta C-13 = -28.7 parts per thousand to -28.1 parts per thousand, delta D = -348 parts per thousand to -345 parts per thousand) and terrestrial C-3 higher plants (delta C-13 = -41.5 parts per thousand to -31.7 parts per thousand, delta D = -352 parts per thousand to -295 parts per thousand, for phytol; delta C-13 = -38.6 parts per thousand to -28.0 parts per thousand, delta D = -283 parts per thousand to -225 parts per thousand for 24-ethylcholest-5-en-3 beta-ol). These results suggest that terrestrially derived phytol and sterols potentially contribute to the side chain of pyropheophytin a and steryl chlorin esters, respectively. (c) 2007 Elsevier Ltd. All rights reserved.
  • Yoshito Chikaraishi, Yuichiro Kashiyamal, Nanako O. Ogawa, Hiroshi Kitazato, Naohiko Ohkouchi
    MARINE ECOLOGY PROGRESS SERIES 342 85 - 90 2007年 [査読有り][通常論文]
     
    We investigated the nitrogen isotopic compositions of individual amino acids from brown and red macroalgae and gastropods in a natural marine coastal environment, to further evaluate them as a tool for ecological studies and to understand the factor(s) controlling the isotopic compositions in terms of biosynthetic and metabolic processes. The isotopic compositions of 12 amino acids range from -2.1 to +8.4 parts per thousand for brown algae, from -3.3 to +12.9 parts per thousand for red algae, and from -0.6 to +16.6 parts per thousand. for gastropods. The isotopic distributions between algae and gastropods and within algal classes are consistent with those in previous reports, suggesting them to be quite useful for studying food web structure. The nitrogen isotopic variation between amino acids strongly reflects their biosynthetic and metabolic processes. In particular, we suggest here that metabolic fate is an important factor in producing distinct trophic relationships in nitrogen isotopic compositions between amino acids.
  • N. Ohkouchi, M. Toyoda, Y. Yokoyama, H. Miura, Y. Chikaraishi, H. Tokuyama, H. Kitazato
    GEOCHIMICA ET COSMOCHIMICA ACTA 70 18 A453 - A453 2006年08月 [査読有り][通常論文]
  • Yoshito Chikaraishi, Hiroshi Naraoka
    CHEMICAL GEOLOGY 231 3 190 - 202 2006年07月 [査読有り][通常論文]
     
    Stable carbon (delta C-13) and hydrogen (delta D) isotopic compositions of n-alkanes, anteiso-alkanes, n-alkanoic acids, n-atkanols, phytol and sterols in raw leaves of Acer argutum and Acer carpinifolium, their fallen leaves, mold and soils from a natural Acer forest were measured in order to: (1) understand isotopic variation of the plant biomarkers in a plant-soil system and (2) evaluate which biomarker is the most effective recorder of soil vegetation. Long-chain (> C-24) n-alkanes, n-alkanoic acids and n-alkanols are gradually enriched in C-13 up to 12.9 parts per thousand (average of 4.3 parts per thousand) and depleted in D up to 94 parts per thousand (average of 55 parts per thousand) from raw leaves to soils. However, anteiso-alkanes, phytol and sterols show little variation in both delta C-13 (<+/- 1%.) and delta D (<+/- 2%.) from raw leaves to soils. These isotope signatures in a plant-soil system indicate that isoprenoid plant biomarkers such as sterols in soils faithfully preserve the isotopic compositions of dominant higher plants growing on the soils without a diagenetic effect upon the isotopic compositions. In contrast, long-chain n-alkyl molecules in soils undergo specific isotopic modification during biodegradation associated with early diagenesis and/or a significant contribution from heterotrophic reworking. (c) 2006 Elsevier B.V. All rights reserved.
  • Yaeko Suzuki, Takashi Korenaga, Yoshito Chikaraishi
    CHEMISTRY LETTERS 35 5 532 - 533 2006年05月 [査読有り][通常論文]
     
    We demonstrated a novel identification method of illegal diesel fuel by using a deuterium (D) labeled n-alkane ([1-D] n-alkane) as a new chemical marker instead of coumarin. In a mixing system of diesel fuel with marker-labeled kerosene, kerosene content is quantitatively determined by D-enrichment of a target n-alkane in a mixed oil using compound-specific stable hydrogen isotope analysis. Thus, [1-D] n-alkane will become a high potential chemical marker instead of coumarin.
  • Yaeko Suzuki, Shintaro Ishioka, Takashi Korenaga, Yoshito Chikaraishi
    Environmental sciences : an international journal of environmental physiology and toxicology 13 4 207 - 12 2006年 
    In this study, we demonstrated a new identification method of illegal diesel fuel using adamantane (tricyclo[3,3,1,1,(3,7)]decane) or [1, 2-D(2)] n-tetradecane as a potential chemical marker instead of coumarin. In a mixing system of diesel fuel with marker-labeled kerosene, the concentration of kerosene in the mixed oil is quantitatively determined using specific ion fragments of the markers using GC/MS analysis, in which the detection limit is 12.5 ng/microl for adamantane or 7.1 ng/microl for [1, 2-D(2)] n-tetradecane. Coumarin, the currently used chemical marker, can be easily removed by sulfuric acid treatment, which is a primal cause of environmental pollution due to the illicit disposal of the strong acidic by-product. However, adamantane and [1, 2-D(2)] n-tetradecane cannot be removed by sulfuric acid treatment. Thus, although the detection limit of adamantane and [1, 2-D(2)] n-tetradecane is higher by approximately one or two orders of magnitude than that of coumarin, they cannot be removed by sulfuric acid treatment. Therefore, adamantane and [1, 2-D(2)] n-tetradecane are strong candidates as potential markers instead of coumarin, leading to the prevention of the production of illegal diesel fuel and a reduction in environmental pollution.
  • Y Chikaraishi
    ORGANIC GEOCHEMISTRY 37 4 428 - 436 2006年 [査読有り][通常論文]
     
    Carbon (delta C-13) and hydrogen isotopic compositions (delta D) of sterols in natural marine brown (Sargassum filicinum and Undaria pinnatifida), red macroalgae (Binghamia californica and Gelidium japonica), and in shellfish (Binghamia californica, Haliotis discus and Omphalius pfeifferi) feeding on the brown algae have been investigated as a first attempt to understand the isotopic compositions of sterols in natural algae and heterotrophs. Brown algae have 24-methylcholesta-5,24(28)-dien3 beta-ol with delta C-13 value of -19.1 +/- 0.1 parts per thousand and delta D value of -298 +/- 4 parts per thousand, and 24-ethylcholesta-5,24(28)E-dien-3 beta-ol with delta C-13 value of -20.3 +/- 0.2 parts per thousand and delta D value of -301 +/- 1 parts per thousand. Red algae have cholest-5-en-3 beta-ol with delta C-13 value of -20.9 +/- 3.0 parts per thousand and delta D value of -289 +/- 0 parts per thousand. The delta C-13 and delta D values of these sterols in algae are consistent with those of algal sterols found in marine sediments, suggesting that the isotopic compositions of algal sterols are well preserved in sediments with little change due to heterotrophic effects. The three shellfish have a wide diversity of sterol types but most sterols, except cholest-5-en-3 beta-ol, have quite similar isotope compositions (delta C-13 value of -19.5 +/- 0.4 parts per thousand and delta D value of -296 +/- 5 parts per thousand) to the dietary algal sterols. On the other hand, cholest-5-en-3 beta-ol is slightly depleted in C-13 by up to 1.7 parts per thousand and significantly enriched in D by up to 49 parts per thousand relative to the other shellfish sterols. This may suggest that shellfish sterols are derived from dietary algal sterols with no substantial isotopic fractionation during either assimilation or modification, but cholest-5-en-3 beta-ol is derived from an admixture of processes including de novo biosynthesis in shellfish. (c) 2005 Elsevier Ltd. All rights reserved.
  • Florian Rommerskirchen, Anna Plader, Geoffrey Eglinton, Yoshito Chikaraishi, Juergen Rullkoetter
    ORGANIC GEOCHEMISTRY 37 10 1303 - 1332 2006年 [査読有り][通常論文]
     
    Grasses (Poaceae) are distributed across the world in broad latitudinal belts and are an important source of C-4 biomass in the geological record of soils as well as lake and marine sediments. We examined long-chain leaf wax components of thirty-five C-4 grasses of the subfamilies Aristidoideae, Chloridoideae and Panicoideae from the southern African grasslands and savannas and three C-3 grasses of the subfamily Pooideae from Peru and Australia and review the relevant botanical, phytogeographic and leaf wax compositional background information. Contents, distribution patterns and molecular stable carbon isotopic compositions of long-chain n-alkanes (n-C-27 to n-C-35) and nalkan-1-ols (n-C-22 to n-C-32) were used to estimate the chemotaxonomic relevance of wax signatures of whole plants, separately for different subfamilies and for members of the three C-4 subtypes (NADP-ME, NAD-ME and PCK). Two grass species were separated into flower heads, leaves and stems and the parts analysed separately. Grass flowers contain remarkable amounts of short-chain n-alkanes, which may have a significant influence on the chemical signature of the whole plant, whereas n-alkanol distribution patterns exhibit no systematics. The stable carbon isotopic composition of both biomarker types in different plant parts is remarkably uniform. Chemotaxonomic differentiation was not possible on a species level based on whole plant samples, but was more successful for averages of subfamily and photosynthetic subtype data. Wax signatures of C-4 grasses are generally distinguishable from those of C-3 species by heavier isotopic values, higher contents of n-C-31 and n-C-33 alkanes and the abundance of the n-C-32 n-alkanol, which is largely absent in C-3 grass waxes. Especially the waxes of the NAD-ME and PCK C-4-subtype grasses, which thrive in extremely and tropical and subtropical areas, contain high relative amounts of longer-chain n-alkane homologues. The chemical classification on a subfamily level, which is in agreement with previously reported subfamilial phylogeny of grasses, implies an evolutionary wax adaptation of C-4 grasses to warm and and habitats. Our results confirm the validity of the contents, distribution patterns and molecular stable carbon isotopic compositions of long-chain n-alkanes and alkan-1-ols as indirect proxies of continental climate conditions in environmental studies of the tropics. (c) 2006 Elsevier Ltd. All rights reserved.
  • Y Chikaraishi, Y Yamada, H Naraoka
    LIMNOLOGY AND OCEANOGRAPHY 50 6 1763 - 1770 2005年11月 [査読有り][通常論文]
     
    The sources (marine algae, terrestrial C3 and C4 plants) of sterols deposited to sediments along a riverine-marine transect from Ohtsuchi River in Iwate Prefecture, Japan, to the northwestern Pacific Ocean were estimated using carbon (delta C-13) and hydrogen isotopic compositions (delta D) in surface sediments. In marine sediments, algal sterols such as 24-methylcholesta-5,22-dien-3 beta-ol had delta C-13 values of -22.7 +/- 0.4 parts per thousand and delta D values of -292 +/- 3 parts per thousand. In contrast, sterols derived from multiple potential sources, such as 24-methylcholest-5-en-3 beta-ol and 24-ethylcholest5-en-3 beta-ol, were gradually enriched in C-13 from riverine (-30.7 parts per thousand and -30.5 parts per thousand, respectively) to marine sediments (-22.3 parts per thousand and -24.4 parts per thousand, respectively), but showed little variation in delta D values (-262 +/- 1 parts per thousand). These isotopic signatures suggest that 24-methylcholest-5-en-3 beta-ol and 24-ethylcholest-5-en-3 beta-ol are derived from C3 plants (similar to 90%) and C4 plants (similar to 10%) in the riverine sediments, and marine algae (similar to 30%), C3 plants (similar to 30%), and C4 plants (similar to 40%) in the open marine sediments. Thus, dual isotopic compositions (delta C-13-delta D) of sterols allow determinations of the proportions of three biological sources, in which the relative contribution of C3 plants decreases while that of marine algae and C4 plants increases from riverine to marine sediments. These results indicate that delta C-13-delta D signatures of sterols provide a useful tool for interpreting the sources of sedimentary organic matter and for understanding the transport and mixing processes of distinct biological sources in riverine-marine environments.
  • Chikaraishi Y, Naraoka H
    Geochimica et Cosmochimica Acta 69 13 3285 - 3297 2005年07月 [査読有り][通常論文]
     
    Organic materials in lacustrine sediments are from multiple terrestrial and aquatic sources. In this study, carbon (delta C-13) and hydrogen isotopic compositions (delta D) of phytol, various sterols, and major n-fatty acids in sediments at Lake Haruna, Japan, were determined in their solvent-extractable (free) and saponification-released forms (bound). The delta C-13-delta D distributions of these lipid molecules in sediments are compared with those of terrestrial C3 and C4 plants, aquatic C3 plants, and plankton to evaluate their relative contributions. delta C-13-delta D of free-phytol in sediments is very close to that of phytol in plankton samples, whereas delta C-13-delta D of bound phytol in sediments is on a mixing line between terrestrial C3 plant and plankton material. Unlike phytol, no significant delta C-13-delta D difference between free and bound forms was found in sterols and n-fatty acids. delta C-13-delta D values of algal sterols such as 24-methylcholesta-5,22-dien-3 beta-ol in sediments are close to those of plankton, whereas delta C-13-delta D of multiple-source sterols such as 24-ethylcholest-5-en-3 beta-ol and of major n-fatty acids such as n-hexadecanoic acid in sediments are between those of terrestrial C3 plants and plankton samples. Thus, delta C-13-delta D distributions clearly indicate the specific source contributions of biomarkers preserved in a lacustrine environment. Free phytol and algal sterols can be attributed to phytoplankton, and bound phytol, multiple source sterols, and major n-fatty acids are contributed by both terrestrial C3 plants and phytoplankton. Copyright (C) 2005 Elsevier Ltd.
  • Chikaraishi Y, Matsumoto K, Ogawa NO, Suga H, Kitazato H, Ohkouchi N
    Phytochemistry 66 8 911 - 920 8 2005年04月 [査読有り][通常論文]
  • Y Chikaraishi, Y Suzuki, H Naraoka
    PHYTOCHEMISTRY 65 15 2293 - 2300 2004年08月 [査読有り][通常論文]
     
    Compound-specific hydrogen isotopic compositions (deltaD) of saturated, monounsaturated and polyunsaturated fatty acids have been determined for natural marine macroalgae including two brown algae (Heterokontophyta) and two red algae (Rhodophyta). deltaD values of individual fatty acids from four macroalgae exhibit a wide variation ranging from -189parts per thousand to +487parts per thousand. Generally, stearic (18:0), arachidic (20:0) and behenic acids (22:0) are much more enriched in D by up to similar to180parts per thousand relative to myristic (14:0), palmitic (16:0), octatetraenoic [18:4(n-3)] and eicosapentaenoic acids [20:5(n-3)]. Other fatty acids such as oleic [18:1(n-9)], lenoleic [18:2(n - 6)] and linolenic acids [18:3(n - 3)] fall isotopically between these fatty acids. This wide deltaD variation of fatty acids is probably explained by the hydrogen isotopic fractionation during desaturation being much larger than that during elongation in the network of polyunsaturated fatty acid biosynthesis. A large hydrogen isotopic fractionation during desaturation may cause D-enrichment in the remaining hydrogen of the residual fatty acids, which could be controlled by the relative flux into their desaturates. (C) 2004 Elsevier Ltd. All rights reserved.
  • Y Chikaraishi, H Naraoka, Poulson, SR
    PHYTOCHEMISTRY 65 10 1369 - 1381 2004年05月 [査読有り][通常論文]
     
    Compound-specific hydrogen and carbon isotopic compositions in n-alkanoic acids, phytol and sterols were determined for various plant classes (terrestrial C3-angiosperm; C3-gymnosperm; C4; crassulacean acid metabolism (CAM); and aquatic C3 plants) in order to investigate isotopic fractionations among various plant classes. In all plants, lipid biomolecules are depleted in both D (up to 324%,) and C-13 (Up to 14.7parts per thousand) relative to ambient water and bulk tissue, respectively. In addition, the magnitude of D- and C-13-depletion of lipid biomolecules is distinctive depending on plant classes. For example, C3 angiosperm n-alkanoic acids are less depleted in D (95 +/- 23parts per thousand) and C-13 (4.3 +/- 2.5parts per thousand) relative to ambient water and bulk tissue, respectively, while C4 plant n-alkanoic acids are more depleted in D (119 +/- 15parts per thousand) and C-13 (10.2 +/- 2.0parts per thousand). On the other hand, C3 angiosperm phytol and sterols are much more depleted in D (306 +/- 12parts per thousand for phytol, 211 +/- 15parts per thousand for sterol) with less depletion in C-13 (4.1 +/- 1.1parts per thousand for phytol, 1.3 +/- 0.9parts per thousand for sterol) relative to ambient water and bulk tissue, respectively, while C4 plant phytol and sterols are less depleted in D (254 +/- 7parts per thousand for phytol, 186 +/- 13parts per thousand for sterols) with much more depletion in C-13 (9.0 +/- 1.2parts per thousand for phytol, 5.0 +/- 1.1parts per thousand for sterols). Among various plant classes, there is a positive correlation between the D- and C-13-depletion for n-alkanoic acids, while a negative correlation was found for phytol and sterols from the same plants. (C) 2004 Elsevier Ltd. All rights reserved.
  • Y Chikaraishi, H Naraoka, Poulson, SR
    PHYTOCHEMISTRY 65 3 323 - 330 2004年02月 [査読有り][通常論文]
     
    Compound-specific carbon and hydrogen isotopic compositions of lipid biomolecules (n-alkanes, n-alkanoic acids, n-alkanols, sesquiterpenes, diterpenes, phytol, diterpenols and beta-sitosterol), extracted from Cryptomeria japonica leaves, were determined in order to understand isotopic fractionations occurring during lipid biosynthesis in this species. All lipid biomolecules were depleted in both C-13 and D relative to bulk tissue and ambient water, respectively. n-Alkyl lipids associated with the acetogenic pathway were depleted in C-13 relative to bulk tissue by 2.4-9.9parts per thousand. and depleted in D relative to ambient water by 91-152parts per thousand. C-15- and C-30- isoprenoid lipids (sesquiterpenes, squalene and beta-sitosterol) associated with the mevalonic-acid pathway are depleted in C-13 relative to bulk tissue by 1.7-3.1parts per thousand. and depleted in D relative to ambient water by 212-238parts per thousand. C-20-isoprenoid lipids (phytol and diterpenoids) associated with the non-mevalonic-acid pathway were depleted in 13C relative to bulk tissue by 4.6-5.9parts per thousand and depleted in D relative to ambient water by 238-303parts per thousand. Phytol was significantly depleted in D by amounts up to 65parts per thousand relative to other C-20 isoprenoid lipids. The acetogenic, mevalonic-acid and non-mevalonic-acid pathways were clearly discriminated using a cross-plot between the carbon and hydrogen isotopic fractionations. (C) 2003 Elsevier Ltd. All rights reserved.
  • Chikaraishi Y, Naraoka H
    Phytochemistry 63 3 361 - 371 2003年06月 [査読有り][通常論文]
     
    Stable hydrogen and carbon isotopic compositions of individual n-alkanes were determined for various terrestrial plants (33 samples including 27 species) and aquatic plants (six species) in natural environments from Japan and Thailand. In C3 plants, n-alkanes extracted from angiosperms have a deltaD value of -152+/-26parts per thousand (relative to Standard Mean Ocean Water [SMOW]) and delta(13)C value of -36.1+/-2.7parts per thousand (relative to Peedde Belemnite [PDB]), and those from gymnosperms have a deltaD value of -149+/-16parts per thousand and delta(13)C value of -31.6+/-1.7parts per thousand. Angiosperms have n-alkanes depleted in C-13 relative to gymnosperms. n-Alkanes from C4 plants have a deltaD value of - 171+/-12parts per thousand and delta(13)C value of -20.5+/-2.1parts per thousand, being a little depleted in D and much enriched in C-13 compared to C3 plants. n-Alkanes of CAM plants are a little depleted in D and vary widely in 813 C relative to those of C3 and C4 plants. In aquatic plants, n-alkanes from freshwater plants have a deltaD value of -187+/-16parts per thousand and delta(13)C value of -25.3+/-1.9parts per thousand, and those from seaweeds have a deltaD value of - 155+/-34parts per thousand and delta(13)C value of -22.8+/-1.0parts per thousand. All n-alkanes from various plant classes are more depleted in D and C-13 relative to environmental water and bulk tissue, respectively. In addition, the hydrogen and carbon isotopic fractionations during n-alkane synthesis are distinctive for these various plant classes. While C3 plants have smaller isotopic fractionations in both D and C-13 seaweed has larger isotopic fractionations. (C) 2003 Elsevier Science Ltd. All rights reserved.
  • Y Chikaraishi, H Naraoka
    GEOCHEMICAL JOURNAL 35 6 451 - 458 2001年 [査読有り][通常論文]
     
    Stable isotopic compositions of organic hydrogen (deltaD) have positive correlations (r(2) > 0.95) with those of carbon (delta C-13) among several compound fractions of terrestrial planet leaves possessing distinctive photosynthetic pathways (C-3, C-4 and CAM). The deltaD/delta C-13 slopes of C-3 plants vary from similar to 25 to 42, which are larger than those of C-4 plants (11 to 12). CAM plants have: intermediate deltaD/delta C-13 slopes (similar to 17 to 20) between C-3 and C-4 plants. Using a deltaD-delta C-13 diagram, photosynthetic metabolisms are clearly discriminated, even though they sometimes cannot be distinguished from each other only by carbon isotopes. Relative to bulk organic matter, hydrogen and carbon of lipid fraction are more depleted in C-13 than those of pigment fraction, respectively. Furthermore, deltaD values of lipid and pigment fractions relative to bulk organic hydrogen have negative correlations with delta C-13 values of corresponding fractions among the, three photosynthetic pathways. This isotopic covariance among each fraction may be attributable to kinetically-controlled molecular biosyntheses using similar enzymes but with different isotope fractionations. Or the intermediate molecules for the biosyntheses have isotopically different pools in hydrogen and carbon.

その他活動・業績

  • 布浦 拓郎, 力石 嘉人, 跡見 晴幸 現代化学 = Chemistry today (569) 57 -61 2018年08月 [査読無し][通常論文]
  • 土屋正史, 宮脇省次, 力石嘉人, 小栗一将, 豊福高志, 多米晃裕, 植松勝之, 竹田晃治, 坂井宥哉, 三宅裕志, 大河内直彦, 丸山正 日本古生物学会年会講演予稿集 2015 19 2015年06月26日 [査読無し][通常論文]
  • 板橋悠, 高野淑識, 力石嘉人, 小川奈々子, 大河内直彦, 山根雅子, 横山祐典, 米田穣 日本文化財科学会大会研究発表要旨集 32nd 2015年
  • 長井裕季子, 豊福高志, 野牧秀隆, 力石嘉人, 和辻智郎, 生田哲郎, 高木善弘, 吉田尊雄, 滋野修一, 井上広滋, 小西正朗 日本地球惑星科学連合大会予稿集(Web) 2015 ROMBUNNO.BPT24‐06 (WEB ONLY) 2015年 [査読無し][通常論文]
  • 布浦 拓郎, 高木 善弘, 力石 嘉人, 森 浩二, 佐藤 喬章, 原田 健史, 柳川 勝紀, 首藤 彩, 大河内 直彦, 跡見 晴幸, 藤田 信之, 高井 研 日本微生物生態学会講演要旨集 2014 88 -88 2014年 [査読無し][通常論文]
  • 野牧秀隆, 力石嘉人, 土屋正史, 豊福高志, 大河内直彦, 植松勝之, 多米晃裕, 北里洋 日本古生物学会年会講演予稿集 2013 24 2013年06月28日 [査読無し][通常論文]
  • アミノ酸窒素同位体比を用いた、陸域分解系における土壌動物の資源利用解析
    陀安一郎, 長谷川尚志, 由水千景, 力石嘉人, 小川奈々子, 大河内直彦 日本生態学会第60回大会 2013年 [査読無し][通常論文]
  • 高橋幸愛, 三宅裕志, 力石嘉人, 土屋正史, 渡部裕美, 丸山正, 藤倉克則 ブルーアース要旨集 2013 72 2013年 [査読無し][通常論文]
  • 鈴木彌生子, 力石嘉人, 山田桂大, 吉田尚弘 日本分析化学会年会講演要旨集 61st 87 2012年09月05日 [査読無し][通常論文]
  • 米田 穣, 覚張 隆史, 内藤 裕一, 力石 嘉人, 大河内 直彦 日本地球化学会年会要旨集 59 (0) 2012年 [査読無し][通常論文]
     
    遺跡から出土する古人骨や動物骨には、生前の生活に関する様々な痕跡が残されている。これらの情報は、物質文化を中心に研究がすすめられてきた考古学では得られない様々な人間活動の直接的な証拠として、近年注目を集めている。本報告では、縄文時代の古人骨、動物骨における地球化学的な分析から、現在どのような議論が行われているかを紹介し、新たな分析手法の応用の可能性について議論したい。縄文時代は、温暖化した完新世の環境のなかで農耕や牧畜といった食料生産を主要な生業にすることなく適応することができた定住的な社会として注目されている。1万年以上にわたる期間、亜寒帯から温帯、亜熱帯にまで拡散した縄文文化をもった人類集団の生業活動について、その多様性や地域性を同位体生態学的な視点から検討する。また、アミノ酸レベルでの同位体分析から見えてきた新しい生活様式についても紹介する。
  • 古人骨および動物遺存体のアミノ酸窒素同位体比分析について
    内藤裕一, 力石嘉人, 大河内直彦, 米田 穣 佐久考古通信 111 17 -18 2012年 [査読無し][通常論文]
  • 山口 保彦, 高野 淑識, 力石 嘉人, 菅 寿美, 小川 奈々子, 横山 祐典, 大河内 直彦 日本地球化学会年会要旨集 59 (0) 2012年 [査読無し][通常論文]
     
    本研究では、2009年の地球深部探査船「ちきゅう」の訓練期間中に房総半島沖で掘削された海洋堆積物コア試料(掘削深度230mbsf)について、全加水分解性アミノ酸および間隙水中溶存態アミノ酸に分け、D/L比と化合物レベル窒素同位体組成の深度分布を報告する。全加水分解性アミノ酸と比較して、間隙水中溶存態アミノ酸D/L比はアラニンでは一貫して高く、グルタミン酸では近い値を示した。アミノ酸窒素同位体組成に関しても、アラニンでは間隙水中溶存態アミノ酸が一貫して高い値を示し、グルタミン酸では全加水分解性と間隙水中溶存態のアミノ酸が近い値を示した。これらの結果を、他の化学成分(アンモニア、硫酸、メタンなど)の濃度分布や、アミノ酸窒素同位体組成に関する微生物培養実験の結果と合わせ、海洋堆積物深部におけるアミノ酸および有機物の動態に関して議論する。
  • アミノ酸窒素同位体比による陸域腐食食物網解析の試み
    長谷川尚志, 力石嘉人, 小川奈々子, 大河内直彦, 陀安一郎 2012年 [査読無し][通常論文]
  • 高橋 幸愛, 藤倉 克則, 三宅 裕志, 力石 嘉人, 土屋 正史, 渡部 裕美, 丸山 正 日本地球化学会年会要旨集 59 (0) 187 -187 2012年 [査読無し][通常論文]
     
    深海化学合成生態系に固有なシンカイヒバリガイ属Bathymodiolus二枚貝は外套腔にエラウロコムシ亜科Branchipolynoe の多毛類を共生させている.本研究ではエラウロコムシ類のサイズ,性比,食性からエラウロコムシ類の生活史や宿主との相互作用の解明を目的とした.相模湾初島沖,沖縄トラフの試料を使用,共生率を推定し,グルタミン酸,フェニルアラニンのアミノ酸窒素同位体比から栄養段階を推定,両種の被食-捕食関係を推定した.エラウロコムシ類の栄養段階は,共生する9 mm以下の個体は約2.6,共生する9 mm以上の個体は約2.2, 宿主は約1.1であったことからネッスイエラウロコムシは体長9 ~10 mmを境に宿主への長期的な共生を開始し,宿主を摂食し始めると推測された.
  • 大河内 直彦, 小川 奈々子, 力石 嘉人 科学 81 (7) 621 -623 2011年07月 [査読無し][通常論文]
  • 縄文人の食性:新しい方法論からの視点
    大河内直彦, 内藤裕一, 力石嘉人, 米田 穣 科学 81 (11) 1116 -1117 2011年 [査読無し][通常論文]
  • 山口 保彦, 高野 淑識, 力石 嘉人, 小川 奈々子, 井町 寛之, 菅 寿美, 横山 祐典, 大河内 直彦 日本地球化学会年会要旨集 58 (0) 92 -92 2011年 [査読無し][通常論文]
     
    アミノ酸窒素同位体組成を環境中微生物代謝の指標として確立すべく、3ドメインを含む5種類の微生物を、特定の窒素源のもとで培養し、そのアミノ酸窒素同位体組成を調べた。すると、微生物がアミノ酸を新規合成する条件では、藻類等と似たアミノ酸窒素同位体組成相対パターンを示し、微生物がアミノ酸を培地から取り込む条件では、動物と近い15N濃縮係数を示した。温度、pH、塩分など生育環境の影響は見られなかった。つまりアミノ酸窒素同位体組成 のパターン・変動ルールが、三つのドメインにまたがる様々な生物間で共通である可能性が示唆された。また、日本近海(秋田沖、房総半島沖など)で海底堆積物を採取し、様々な画分(全加水分解成分、遊離成分など)のアミノ酸の量・組成・窒素同位体組成を分析した。それらの結果を、上記培養実験の結果をもとに解釈し、海底堆積物中の微生物代謝を推察した。
  • 陸域腐食食物網へのアミノ酸窒素同位体比の適用
    長谷川尚志, 力石嘉人, 小川奈々子, 大河内直彦, 陀安一郎 日本生態学会第58回大会 2011年 [査読無し][通常論文]
  • 力石 嘉人, 小川 奈々子, 高野 淑識, 土屋 正史, 大河内 直彦 地球化学 44 (4) 233 -241 2010年12月25日 [査読無し][通常論文]
     
    Nitrogen isotopic composition (δ^<15>N) of individual amino acids has recently been employed as a potential powerful method for estimating the trophic level of organisms in food webs. In metabolic processes, one group of amino acids has little change in their nitrogen isotopic composition (e.g., 0.4‰ for phenylalanine), although another group has a large isotopic fractionation (e.g., 8.0‰ for glutamic acid). This fractionation could be associated with the cleavage of carbon-nitrogen bond in the metabolic processes (e.g., transamination) of amino acids. Therefore, a comparison between δ^<15>...
  • Sonoda Kazuhiko, Takahashi Masashiro, 力石 嘉人, YAMAMOTO Shuichi Researches in organic geochemistry 26 115 -122 2010年12月24日 
    This study demonstrates the stable carbon isotope analysis of individual lignin phenols based on off-line degradation and derivatization by tetramethylammonium hydroxide (TMAH) thermochemolysis, semi-purification by high-performance liquid chromatography (HPLC), compound-specific isotope analysis (CSIA) by gas chromatography/combustion/isotope ratio mass spectrometry (GC/C/IRMS), and isotope effect correction by isotope mass balance calculation. In GC/C/IRMS, we obtained the following optimal conditions to accurately and precisely determine the isotopic composition: combustion temperature of 1000℃, He carrier flow rate of 1.6mL min^<-1>, and injection amount of lignin phenols of 30-140ng. HPLC semi-purification using a normal-phase silica column with a column oven (at 30℃) can achieve baseline-separation of individual lignin phenols on the GC chromatogram without isotopic fractionation. Isotopic fractionation during TMAH derivatization can be corrected by the logarithmic correlation between the isotopic composition of the incorporated carbon during TMAH derivatization and the ratio of relative abundance between lignin phenols and TMAH reagents. By using this method, the carbon isotopic composition of individual lignin phenols can be determined within a standard deviation (1σ) of 0.2‰-0.9‰, making this method suitable for molecular isotope studies in the field of organic geochemistry.
  • 高野 淑識, 力石 嘉人, 大河内 直彦 Researches in organic geochemistry 26 81 -93 2010年12月24日 
    Recent advances in the application of molecular approaches have emphasized our potentially underestimate of microbial diversity in natural environments and have revealed comprehensive biogeochemical processes. One of the biggest challenges for organic geochemists and/or microbial ecologists is to identify which organisms are carrying out a specific set of metabolic processes. To answer this fundamental question, stable isotope probing (SIP) together with compound-specific isotope analysis (CSIA) is a useful technique to understand the microbial ecology and its biogeochemical cycles. The method relies on the incorporation of a substrate that is highly enriched in a stable isotope such as ^<13>C and ^<15>N, and the identification of specific molecular targets through active microorganisms in any environment. However, we have to pay attention about highly SI-enriched contamination problems and co-elution problems during pretreatment of chemical analysis and also in chromatographic procedures, which potentially prevent us from performing precise CSIA. Here, we point out quality control by wet chemical pre-treatment for precise compound-specific isotope analysis by isotope-ratio mass spectrometry coupled to gas chromatography and liquid chromatography. Not only in biogeochemical background but also from a scope of common welfare, CSIA technique is also widely useful tools for validation approaches in food material, anti-doping test, and environmental assessment. For further precise CSIA, we also discuss representative optimized analytical conditions of some model compounds including intact polar lipids (IPLs) with its derivatives, n-alkane, and amino acids.
  • J. Tyler, Y. Kashiyama, N. Ohkouchi, N. Ogawa, Y. Yokoyama, Y. Chikaraishi, R.A. Staff, M. Ikehara, C. Bronk Ramsey, C. Bryant, F. Brock, K. Gotanda, T. Haraguchi, H. Yonenobu, T. Nakagawa, Suige, Project Members Geochemistry Geophysics Geosystems 11 Q09010 2010年09月 [査読無し][通常論文]
  • Isotopomers of chlorophyll nuclei: Theory and application
    N. Ohkouchi, Y. Chikaraishi, Y. Kashiyama, N.O. Ogawa In: N.Ohkouchi I. Tayasu K. Koba (eds.) Earth Life and Isotopes Kyoto University Press Kyoto 271 -290 2010年08月 [査読無し][通常論文]
  • Reconstructing the life history of modern and fossil nautiloids based on the nitrogen isotopic composition of shell organic matter and amino acids
    Y. Kashiyama, N.O. Ogawa, Y. Chikaraishi, N. Kashiyama, S. Sakai, K. Tanabe, N. Ohkouc In: K. Tanabe Y. Shigeta T. Sasaki H. Hirano (eds.) Cephalopod-Present and Past 67 -75 2010年05月 [査読無し][通常論文]
  • 坪井 美里, 佐藤 蓉子, 浜名 徳明, 中村 栄子, 間嶋 隆一, 北里 洋, 菅 寿美, 力石 嘉人, 加藤 和浩, 和田 秀樹, 大河内 直彦 化石 87 (0) 5 -21 2010年 [査読無し][通常論文]
     
    We analyzed lipid biomarkers related to AOM (anaerobic oxidation of methane) that happened in the early Pleistocene (1.7-1.4Ma) cold-seep site, northern part of Miura Peninsula, Pacific side of central Japan. Nineteen samples are obtained from a bedding-normal, 107m-long core consisting of the Koshiba (sandy mudstone and muddy sandstone, above 23m in core depth) and the Ofuna (mudstone, below 23m) Formations. In this core, both the chemoautotrophic bivalves (Lucinoma, Conchocele, Archarax) and ^<13>C-depleted authigenic carbonates (aragonite, MG-calcite, dolomite) occur abundantly. Four important results of this study are summarized as follows. 1) Both archaeal and sulfate reducing bacterial (SRB) biomarkers are recovered in all samples and their ether linkages are well preserved even in 1.7-1.4Ma sediments. 2) High activities of AOM are inferred in 7.1-7.6m and 14.6m in core depths where both archaeal and SRB-biomarkers are distinctly concentrated and greatly depleted in ^<13>C (δ^<13>C less than-100‰ vs. PDB). Those activities happened probably when marine bottoms were in 6.5-7m and 13-13.5m, respectively, where chemoautotrophic bivalves occur abundantly. 3) Two samples obtained from the same horizon 14.6m show an apparent difference in biomarker compositions. This difference may be attributed to a different micro habitats for microbes. 4) The occurrences of biomarkers derived from planktonic archaea are inferred from their δ^<13>C values and relative abundance of 4 kinds of biphytanes. Planktonic archaeal biomarkers are probably recovered from all samples and their concentration rates may be useful as an index of sedimentation rate.
  • 山口 保彦, 高野 淑識, 力石 嘉人, 小川 奈々子, 井町 寛之, 菅 寿美, 横山 祐典, 大河内 直彦 日本地球化学会年会要旨集 57 (0) 115 -115 2010年 [査読無し][通常論文]
     
    本研究では、三つのドメイン(真核生物・バクテリア・アーキア)を含む5種類の微生物を、特定の窒素源のもとで培養し、そのアミノ酸窒素同位体組成を調べた。その結果、アミノ酸窒素同位体組成のパターン・変動ルールが、三つのドメインを含む様々な生物間で共通であることが示唆された。つまりアミノ酸窒素同位体組成は、微生物の現場における代謝(アミノ酸の合成もしくは分解)および生物地球化学的役割(特に窒素循環・有機物変質)を調べための、強力な手法になりうるだろう。
  • 土屋 正史, 藤原 義弘, 野牧 秀隆, 豊福 高志, 山本 啓之, 丸山 正, 和田 英太郎, 力石 嘉人, 大河内 直彦, 高野 淑識, 小川 奈々子, 藤倉 克則, 吉田 尊雄, 喜多村 稔, リンジー ドゥーガル 日本地球化学会年会要旨集 57 (0) 41 -41 2010年 [査読無し][通常論文]
     
    海洋生態系は,様々な生物群集からなる構成されており,複雑な被食―捕食の生物間相互作用の上に成立しているため,その構造を明らかにすることは難しい。現在の海洋生態系は,様々な環境変遷を経てきた生物群集から構成されており,このような生物間の相互作用や進化を通して,現在の海洋生態系が形成されている。海洋生態系の構造を明らかにすることは,環境変化に対する生物の応答様式や温暖化に伴う海洋生態系の構造の変化の追跡,あるいは多様性の維持機構を明らかにする上でも非常に重要である。<br> アミノ酸の窒素同位体比に基づく栄養段階の推定法は,複雑な生態系の栄養段階を明瞭に示すことができる重要なツールである。この手法は,海洋研究開発機構で開発された新たなツールであり,栄養段階に伴い食物連鎖の上位の生物ほど15Nの濃縮が見られるアミノ酸(グルタミン酸など)と,栄養段階によらずほぼ一定の窒素同位体比を持つアミノ酸(フェニルアラニンなど)を用いることで,生物の栄養段階を正確に求めることを基盤技術としている。アミノ酸の窒素同位体比の変化は,生物個体内の代謝による同位体分別の影響により,栄養段階の上昇が生じるという生物の生理学的特性に起因しているため,同位体分別の背景を理解した上で栄養段階を推定できることに大きな利点がある。<br> われわれは,アミノ酸の窒素同位体比分析技術を用いて,海洋生態系のダイナミクスと生態系を構成する海洋生物の進化や共生現象を介した環境への適応様式を理解し,資源などのエネルギーが表層から底層への梯子を段階的に連鎖する「梯子モデル」が,どのように成立しているのかを検証する。具体的には,1)海洋生態系の構造を明らかにすること,2)海洋生物の共生系の仕組みを明らかにすることであり,前者では,被食―捕食の関係から食物網構造を明らかにするとともに,生態・生化学・進化生態学的な解析をあわせることで,海洋生態系の構造と役割,進化を明らかにする。後者では,遺伝子からその代謝機能を推定するとともに,共生系内での物質の流れを安定同位体から明らかにし,宿主あるいは共生生物の依存度を明らかにし,共生を介した生態や進化を理解することを目指している。 これまでに,海洋の化学合成生態系や光合成生態系などを構成する真核生物の栄養段階を推定するとともに,共生細菌などの共生生物と宿主との関係を窒素同位体比と遺伝子から得られた代謝機能との関係を推測した。相模湾の底層生態系では,甲殻類などが光合成生態系由来の生物に依存する生物を捕食するとともに,化学合成生態系に依存する生物を捕食する。このように底層生物は複数の生態系に依存した栄養摂取形態を持つと考えられ,各アミノ酸の窒素同位体比は,利用する資源の由来を推測できる可能性がある。また,冷湧水系の化学合成生態系では,海底下からの湧水に依存するため軽い窒素同位体比を持つのに対して,光合成生態系では重い値を示す。アミノ酸窒素同位体比は,各生態系における栄養段階を理解するだけではなく,光合成生物の化学合成系依存の割合を理解することもできる。発表では,相模湾を中心とする海洋生物のアミノ酸窒素同位体の結果とそれを基にした栄養段階について紹介する。
  • 食性指標としてのアミノ酸窒素安定同位体比の利用:土壌食物網研究への適用にむけて
    長谷川尚志, 力石嘉人, 小川奈々子, 大河内直彦, 陀安一郎 日本生態学会第57回大会 2010年 [査読無し][通常論文]
  • 力石 嘉人 Researches in organic geochemistry 25 29 -38 2009年11月30日 
    After the development of compound-specific isotope analysis (CSIA) by gas chromatograph/pyrolysis/isotope ratio mass spectrometer (GC/pyrolysis/IRMS) in the end of the 1990s, stable hydrogen isotopic composition of organic compounds has been employed for many fields of studies, particularly among the organic geochemical community as a powerful tool for tracing sources and delivery of organic compounds in geological and geographical samples and as a potential proxy for reconstructing paleoclimatic, paleohydrological, and paleosalinity changes. However, sample amount required for accurate and precise determination of the isotopic composition is generally 10-50nmol H for each compound, which is much larger than that of stable carbon (0.1-5nmol C) and nitrogen (1-10nmol N) on the isotope analysis by gas chromatograph/combustion/isotope ratio mass spectrometer (GC/combustion/IRMS). Here, I demonstrate the performance of GC/pyrolysis/IRMS on the small amount of samples, and suggest a mathematical correction for preventing systematic errors in the measured isotopic composition due to different sample amounts. By using this correction, the hydrogen isotopic composition of organic compounds can be determined with a standard deviation (1σ) of better than 7‰ on the sample amount of 4nmol H and even 13‰ on the sample amount of 2nmol H. This correction thus allows us easy access to the hydrogen isotopic composition of organic compounds containing with small concentration in samples.
  • 力石 嘉人, 高野 淑識, 大河内 直彦 Researches in organic geochemistry 25 61 -70 2009年11月30日
  • 小川 奈々子, 力石 嘉人, 大河内 直彦 臨床化学 38 (3) 266 -271 2009年07月31日 [査読無し][通常論文]
  • Y. Chikaraishi, N. O. Ogaw, N. Ohkouchi GEOCHIMICA ET COSMOCHIMICA ACTA 73 (13) A219 -A219 2009年06月 [査読無し][通常論文]
  • Dietary reconstruction of Jomon hunter-gatherers based on nitrogen isotopic composition of amino acid
    Naito Y, Chikaraishi Y, Ohkouchi N, Yoneda M The 4th International Symposium on Isotopomers (ISI 2008) Proceedings 4 265 -267 2008年 [査読有り][通常論文]
  • 大河内 直彦, 力石 嘉人, 小川 奈々子, 柏山 祐一郎, 菅 寿美, 北里 洋 日本地球化学会年会要旨集 55 (0) 185 -185 2008年 [査読無し][通常論文]
     
    クロロフィルは光合成独立栄養生物によって合成され,生体内では光合成色素として機能している。このクロロフィルは,光合成細菌が合成するバクテリオクロロフィルまで含めると,大きく10種類に分類することができ,各クロロフィルは特定の起源光合成生物によってのみ合成されることが知られている。このクロロフィルの中心核のテトラピロール構造は,堆積物中で化学的にも微生物学的にも非常に安定したャ泣tィリンと呼ばれる化合物群として長期間保存されている。そのため,堆積岩から抽出されるャ泣tィリンの炭素および窒素安定同位体比は,クロロフィルの同位体組成,ひいては一次生産者の同位体組成を強く反映している。それらの情報は,潜在的に過去の光合成生物の栄養塩の起源,取り込み様式,代謝プロセスといった海洋学的,生物学的な情報を,ほぼ純粋な形で保存していると考えられる。本講演では,主にクロロフィルの分子内同位体組成(アイソトャ}ー)を決定する要因について,生合成の観点から考察し,それからどのような環境情報が引き出せるのかについて論じるとともに,実際の測定結果との整合性についても論じる。クロロフィルのテトラピロール構造は,葉緑体内でグルタミン酸8分子が縮合して生成されるため,その炭素同位体比はグルタミン酸のそれを強く反映したものである。ただし,縮合の過程でグルタミン酸のC5炭素が6つ脱離するため,正確に一致することはない(Ohkouchi et al., 2008)。テトラピロール構造の分子内炭素同位体組成のうち,各ピロール環を架橋している炭素については,クロロフィルを各ピロール環に分解(マレイミド化)することにより,マスバランスによって同位体組成を求めることができる。またクロロフィルの窒素同位体比は,グルタミン酸がアミノレブリン酸になるときに導入されるアンモニアの窒素同位体比を反映している。したがって,グルタミン酸の窒素同位体比とは一致しないはずであり,実際にそのことが実験から確認された。各ピロール環に含まれる窒素は,マレイミド化した後に測定したところ,理論どおりほぼ同じ同位体組成を持つことが明らかになった。
  • 力石 嘉人 Researches in organic geochemistry 22 1 -18 2007年12月28日 
    Gas chromatograph/pyrolysis/isotope ratio mass spectrometer (GC/pyrolysis/IRMS) and pyrolysis elemental analyzer/isotope ratio mass spectrometer (pyrolysis-EA/IRMS) are relatively new instruments for on-line determination of stable hydrogen isotopic composition (D/H) of organic compounds, which allow easy and rapid access to their isotopic composition in various biological and geological samples. The hydrogen isotopic composition is a potential tool for the reconstruction of hydrological cycle in paleoenvironment. Combined with carbon isotopic composition (^<13>C/^<12>C), it has also been used for the evaluation of sources and delivery of organic compounds in geological as well as geographical samples. This paper reviews recent studies on the compound-specific hydrogen isotope analysis of lipids and pigments, which consists of brief summaries of (1) biological controls on the isotopic composition, (2) isotopic modification associated with biodegradation and diagenesis, and (3) its application in organic geochemistry.
  • 藻類・植物・堆積物に含まれるクロロ色素・フェオ色素のHPLC/MSによる解析
    Y. Chikaraishi, Y. Kashiyama, N. Ohkouchi Researches in Organic Geochemistry 22 43 -55 2007年12月 [査読無し][通常論文]
  • 力石 嘉人, 柏山 祐一郎, 小川 奈々子, 大河内 直彦 Radioisotopes 56 (8) 463 -477 2007年08月15日 [査読無し][通常論文]
  • Y. Chikaraishi, Y. Kashiyama, N. O. Ogawa, H. Kitazato, N. Ohkouchi GEOCHIMICA ET COSMOCHIMICA ACTA 71 (15) A170 -A170 2007年08月 [査読無し][通常論文]
  • Y. Kashiyama, N. O. Ogawa, Y. Chikaraishi, S. Nomoto, R. Tada, H. Kitazato, N. Ohkouchi GEOCHIMICA ET COSMOCHIMICA ACTA 71 (15) A466 -A466 2007年08月 [査読無し][通常論文]
  • 力石嘉人, 柏山祐一郎, 小川奈々子, 高野淑識, 菅寿美, 豊福高志, 富谷朗子, 北里洋, 大河内直彦 日本地球化学会年会講演要旨集 54th 158 2007年 [査読無し][通常論文]
  • 大河内 直彦, 柏山 祐一郎, 力石 嘉人, 小川 奈々子, 黒田 潤一郎, 北里 洋 日本地質学会学術大会講演要旨 113 48 -48 2006年09月08日 [査読無し][通常論文]
  • N. Ohkouchi, Y. Kahiyama, Y. Chikaraishi, N. O. Ogawa, R. Tada, H. Kitazato GEOCHIMICA ET COSMOCHIMICA ACTA 70 (18) A452 -A452 2006年08月 [査読無し][通常論文]
  • Y. Kashiyama, N. O. Ogawa, Y. Chikaraishi, H. Suga, R. Tada, H. Kitazato, N. Ohkouchi GEOCHIMICA ET COSMOCHIMICA ACTA 70 (18) A306 -A306 2006年08月 [査読無し][通常論文]
  • Y. Chikaraishi, Y. Kashiyama, N. O. Ogawa, H. Kitazato, S. Nomoto, N. Ohkouchi GEOCHIMICA ET COSMOCHIMICA ACTA 70 (18) A100 -A100 2006年08月 [査読無し][通常論文]
  • 鈴木彌生子, 力石嘉人, 小川奈々子, 大河内直彦, 伊永隆史 分析化学討論会講演要旨集 67th 45 2006年04月29日 [査読無し][通常論文]
  • Stable carbon and nitrogen compositions of photosynthetic pigments as tracers for elemental cycle in the modern- and paleo-environments
    N. Ohkouchi, Y. Nakajima, N.O. Ogawa, H. Suga, Y. Kashiyama, K. Matsumoto, Y. Chikaraishi, K. Oguri, H. Kitazato Frontier Research on Earth Evolution 2 1 -4 2006年 [査読無し][通常論文]
  • 柏山 祐一郎, 小川 奈々子, 力石 嘉人, 菅 寿美, 野本 信也, 多田 隆治, 北里 洋, 大河内 直彦 日本地球化学会年会要旨集 53 (0) 20 -20 2006年 [査読無し][通常論文]
     
    堆積物中から抽出されるポルフィリン化合物(化石ポルフィリン)は、光合成生物が普遍的に合成するクロロフィルやバクテリオクロロフィルを起源とする。よってその安定同位体組成は、過去の環境中の物質循環や、光合成生物の代謝活動を直接的に記録したものであり、過去の海洋表層の物質循環を理解する上で有力な指標となりうる。本研究では、化石ポルフィリンを高速液体クロマトグラフィーを用いて単離・精製し、分析感度を向上させた元素分析計/同位体質量分析計を用いて測定する手法を確立した。また、単離した化石ポルフィリンを酸化分解してマレイミド化を行い、ガスクロマトグラフ/燃焼/同位体質量分析計を用いて、極微量のポルフィリンについても窒素同位体組成を測定することに成功した。また、中部中新統女川層(12~10Ma)及びイタリアの白亜系黒色頁岩(海洋部酸素事変;OAE-2)の分析結果に基づき、堆積当時の海洋環境について論じる。
  • 力石 嘉人, 柏山 祐一郎, 多田 洋平, 豊福 高志, 小川 奈々子, 北里 洋, 大河内 直彦 日本地球化学会年会要旨集 53 (0) 231 -231 2006年 [査読無し][通常論文]
     
    生体試料の全窒素同位体比(SUP15/SUPN/SUP14/SUPN)は、食物連鎖における栄養段階の上昇に伴い約3パーミルずつ高くなることが経験的に知られており、この知見は生態系の食物連鎖網や窒素サイクルの解析に広く用いられてきた。しかし、この窒素同位体比変動(SUP15N/SUP濃縮)の詳細なメカニズムはほとんどわかっていない。BRそこで本研究では、藻類と捕食動物に含まれる12種類のアミノ酸の窒素同位体比を調査した結果から、生体アミノ酸の窒素同位体比変動を明らかにし、食物連鎖における窒素同位体比変動メカニズムを考察した。発表ではさらに、この結果を応用した生態学研究をいくつか紹介し解説する。
  • 力石 嘉人, 奈良岡 浩 ぶんせき (356) 456 -462 2004年08月05日
  • Y Chikaraishi, H Naraoka GEOCHIMICA ET COSMOCHIMICA ACTA 68 (11) A338 -A338 2004年06月 [査読無し][通常論文]
  • Y Chikaraishi GEOCHIMICA ET COSMOCHIMICA ACTA 67 (18) A64 -A64 2003年09月 [査読無し][通常論文]
  • Poulson, SR, Y Chikaraishi, H Naraoka GEOCHIMICA ET COSMOCHIMICA ACTA 67 (18) A382 -A382 2003年09月 [査読無し][通常論文]
  • 奈良岡 浩, 力石 嘉人 Radioisotopes 51 (6) 249 -250 2002年06月15日

教育活動情報

主要な担当授業

  • 大学院共通授業科目(一般科目):自然科学・応用科学
    開講年度 : 2021年
    課程区分 : 修士課程
    開講学部 : 大学院共通科目
    キーワード : 安定同位体, 同位体比質量分析計(IRMS), 水素, 炭素, 窒素, 酸素
  • 古気候変動学特論
    開講年度 : 2021年
    課程区分 : 修士課程
    開講学部 : 環境科学院
    キーワード : -
  • 生態系物質循環学特論
    開講年度 : 2021年
    課程区分 : 修士課程
    開講学部 : 環境科学院
    キーワード : 生物圏,生態系,水循環,炭素循環,窒素循環,安定同位体,地球環境,地球システム,環境 biosphere, ecosystem, water cycle, carbon cycle, nitrogen cycle, stable isotope, global environment, earth system, environment
  • 生態系環境科学特論
    開講年度 : 2021年
    課程区分 : 修士課程
    開講学部 : 環境科学院
    キーワード : Ecosystem, environments, photosynthesis, food webs, stable isotope, organic matter, biogeochemical cycle
  • 環境と人間
    開講年度 : 2021年
    課程区分 : 学士課程
    開講学部 : 全学教育
    キーワード : 大気、海洋、生態系、気候変化、地球環境問題、地球温暖化、成層圏オゾン層破壊、大気汚染


Copyright © MEDIA FUSION Co.,Ltd. All rights reserved.