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NAKADA Takashi

Faculty of Science　Biological Sciences　BiodiversityLecturer

Researcher basic information

■ Degree
  • Doctor, The University of Tokyo, Mar. 2008
■ URL
researchmap URLホームページURL■ Various IDs
Researcher number
  • 10548994
ORCID IDJ-Global ID■ Educational Organization

Research activity information

■ Papers
  • Heterochlamydomonas kakosmos comb. nov. (Volvocales, Chlorophyceae) and its synonymy with H. callunae
    Hotaka Matsuoka; Takashi Nakada
    Phycological Research, 10 Apr. 2026
    Scientific journal
  • Did enigmatic ancient Japanese algal names, Susimwo and Tusimwo, indicate Sargassum fusiforme?
    仲田崇志
    藻類, 74, 2, 2026
  • Studies on the Subheading “Algae” (“Seaweeds” and “Waterweeds”) in the Main Heading “Vegetables” in Wamyo Ruijusho
    仲田崇志
    植物研究雑誌(Web), 101, 1, 2026
  • 江戸後期の大型節用集における藻類関連語の由来と継承
    仲田崇志
    藻類, 72, 1, 2024
  • Aphelidium parallelum, s p. nov., a new aphelid parasitic on selenastracean green algae
    Kensuke Seto; Takashi Nakada; Yuuhiko Tanabe; Masaki Yoshida; Maiko Kagami
    MYCOLOGIA, 114, 3, 544, 555, 04 May 2022
    English, Scientific journal
  • Phytoplankton species abundance in Tokyo Bay (Japan) from 1998 to 2019
    Takashi Nakada; Toshiya Katano; Keigo Hashimoto; Maiko Kagami
    Ecological Research, Sep. 2021
    Scientific journal
  • A non-photosynthetic green alga illuminates the reductive evolution of plastid electron transport systems.
    Motoki Kayama; Jun-Feng Chen; Takashi Nakada; Yoshiki Nishimura; Toshiharu Shikanai; Tomonori Azuma; Hideaki Miyashita; Shinichi Takaichi; Yuichiro Kashiyama; Ryoma Kamikawa
    BMC biology, 18, 1, 126, 126, 16 Sep. 2020, [International Magazine]
    English, Scientific journal, BACKGROUND: Plastid electron transport systems are essential not only for photosynthesis but also for dissipating excess reducing power and sinking excess electrons generated by various redox reactions. Although numerous organisms with plastids have lost their photoautotrophic lifestyles, there is a spectrum of known functions of remnant plastids in non-photosynthetic algal/plant lineages; some of non-photosynthetic plastids still retain diverse metabolic pathways involving redox reactions while others, such as apicoplasts of apicomplexan parasites, possess highly reduced sets of functions. However, little is known about underlying mechanisms for redox homeostasis in functionally versatile non-photosynthetic plastids and thus about the reductive evolution of plastid electron transport systems. RESULTS: Here we demonstrated that the central component for plastid electron transport systems, plastoquinone/plastoquinol pool, is still retained in a novel strain of an obligate heterotrophic green alga lacking the photosynthesis-related thylakoid membrane complexes. Microscopic and genome analyses revealed that the Volvocales green alga, chlamydomonad sp. strain NrCl902, has non-photosynthetic plastids and a plastid DNA that carries no genes for the photosynthetic electron transport system. Transcriptome-based in silico prediction of the metabolic map followed by liquid chromatography analyses demonstrated carotenoid and plastoquinol synthesis, but no trace of chlorophyll pigments in the non-photosynthetic green alga. Transient RNA interference knockdown leads to suppression of plastoquinone/plastoquinol synthesis. The alga appears to possess genes for an electron sink system mediated by plastid terminal oxidase, plastoquinone/plastoquinol, and type II NADH dehydrogenase. Other non-photosynthetic algae/land plants also possess key genes for this system, suggesting a broad distribution of an electron sink system in non-photosynthetic plastids. CONCLUSION: The plastoquinone/plastoquinol pool and thus the involved electron transport systems reported herein might be retained for redox homeostasis and might represent an intermediate step towards a more reduced set of the electron transport system in many non-photosynthetic plastids. Our findings illuminate a broadly distributed but previously hidden step of reductive evolution of plastid electron transport systems after the loss of photosynthesis.
  • Taxonomy and nomenclature of the recently published chlamydomonad genera Ostravamonas and Paludistella (Volvocales, Chlorophyceae)
    TAKASHI NAKADA; HANI SUSANTI
    Phytotaxa, 23 Jun. 2020
    Scientific journal
  • Chlorococcum turfosum comb. nov. (Volvocales, Chlorophyceae) and visualization of chimeric sequences
    Takashi Nakada; Shin Watanabe; Louise A. Lewis; Masaru Tomita
    Phycological Research, Jul. 2019
    Scientific journal
  • Improved taxon sampling and multigene phylogeny of unicellular chlamydomonads closely related to the colonial volvocalean lineage Tetrabaenaceae-Goniaceae-Volvocaceae (Volvocales, Chlorophyceae).
    Takashi Nakada; Yudai Tsuchida; Masaru Tomita
    Molecular phylogenetics and evolution, 130, 1, 8, Jan. 2019, [International Magazine]
    English, Scientific journal, In the green algal order Volvocales (Chlorophyceae), flagellate colonial forms have evolved at least four times. One of these colonial lineages, Tetrabaenaceae-Goniaceae-Volvocaceae (TGV), which belongs to the clade Reinhardtinia, is closely related to several unicellular chlamydomonads in the genera Chlamydomonas and Vitreochlamys. However, the unicellular sister of TGV has not been specified. Here, the largest ever 18S rRNA phylogenetic tree of Reinhardtinia was constructed including several newly isolated chlamydomonads, and a clade (core-Reinhardtinia) including 32 unicellular lineages and three colonial families were recognized. Interrelationships within core-Reinhardtinia were barely resolved in the tree, and therefore combined 18S-atpB-psaA-psaB-psbC-rbcL gene phylogenetic analyses were performed with selected representatives of 29 of the 32 unicellular lineages and three colonial families. The 29 unicellular lineages were clustered into five metaclades and an unassigned lineage; the metaclade that includes Chlamydomonas pila was resolved, with moderate support, as the sister clade to TGV. To examine possible biases from specific gene(s), long-branch taxa, and the heterogeneous base composition, phylogenetic analyses using several smaller data sets were also performed. Light microscopy of C. pila and its relatives indicated that any early steps towards colony evolution appeared after divergence of TGV from the C. pila lineage.
  • Microglena redcarensis sp. nov. (Volvocales, Chlorophyceae), a brackish water chlamydomonad with contractile vacuoles
    Takashi Nakada; Shunsuke Takahashi; Masaru Tomita
    Phycological Research, Oct. 2018
    Scientific journal
  • Morphology and phylogeny of a new wall-less freshwater volvocalean flagellate, Hapalochloris nozakii gen. et sp. nov. (Volvocales, Chlorophyceae).
    Takashi Nakada; Masaru Tomita
    Journal of phycology, 53, 1, 108, 117, Feb. 2017, [International Magazine]
    English, Scientific journal, New strains of a wall-less unicellular volvocalean flagellate were isolated from a freshwater environment in Japan. Observations of the alga, described here as Hapalochloris nozakii Nakada, gen. et sp. nov., were made using light, fluorescence, and electron microscopy. Each vegetative cell had two flagella, four contractile vacuoles, and a spirally furrowed cup-shaped chloroplast with an axial pyrenoid, and mitochondria located in the furrows. Based on the morphology, H. nozakii was distinguished from other known wall-less volvocalean flagellates. Under electron microscopy, fibrous material, instead of a cell wall and dense cortical microtubules, was observed outside and inside the cell membrane, respectively. Based on the phylogenetic analyses of 18S rRNA gene sequences, H. nozakii was found to be closely related to Asterococcus, Oogamochlamys, Rhysamphichloris, and "Dunaliella" lateralis and was separated from other known wall-less flagellate volvocaleans, indicating independent secondary loss of the cell wall in H. nozakii. In the combined 18S rRNA and chloroplast gene tree, H. nozakii was sister to Lobochlamys.
  • Phylogenetic Position and Molecular Chronology of a Colonial Green Flagellate, Stephanosphaera pluvialis (Volvocales, Chlorophyceae), among Unicellular Algae.
    Hidehito Munakata; Takashi Nakada; Kenji Nakahigashi; Hisayoshi Nozaki; Masaru Tomita
    The Journal of eukaryotic microbiology, 63, 3, 340, 8, May 2016, [International Magazine]
    English, Scientific journal, The genus Balticola comprises a group of unicellular green flagellate algae and is composed of four species formerly classified in the genus Haematococcus. Balticola is closely related to a colonial green flagellate, Stephanosphaera pluvialis. Although the phylogeny among these genera was previously investigated based on two nuclear gene sequences, the phylogenetic sister of S. pluvialis has yet to be determined. In the present study, the species diversity of Balticola and Stephanosphaera was investigated using 18S rRNA gene sequences, and phylogenetic analyses of combined nuclear and chloroplast gene sequences were performed to understand the evolutionary origin of coloniality in Stephanosphaera. The divergence times of four colonial volvocalean flagellates from their respective unicellular sisters were also estimated. Six Balticola genotypes and a single Stephanosphaera genotype were recognized, and one Balticola genotype was resolved as the sister of S. pluvialis, showing that Balticola is a nonmonophyletic genus. The divergence time of Stephanosphaera from its nearest Balticola relative was estimated to be 4-63 million years ago, and these genera represent the most recently diverged pair of unicellular and colonial flagellates among the Volvocales.
  • Taxonomic revision of Chlamydomonas subg. Amphichloris (Volvocales, Chlorophyceae), with resurrection of the genus Dangeardinia and descriptions of Ixipapillifera gen. nov. and Rhysamphichloris gen. nov.
    Takashi Nakada; Masaru Tomita; Jiunn-Tzong Wu; Hisayoshi Nozaki
    Journal of phycology, 52, 2, 283, 304, Apr. 2016, [International Magazine]
    English, Scientific journal, Chlamydomonas (Cd.) is one of the largest but most polyphyletic genera of freshwater unicellular green algae. It consists of 400-600 morphological species and requires taxonomic revision. Toward reclassification, each morphologically defined classical subgenus (or subgroup) should be examined using culture strains. Chlamydomonas subg. Amphichloris is characterized by a central nucleus between two axial pyrenoids, however, the phylogenetic structure of this subgenus has yet to be examined using molecular data. Here, we examined 12 strains including six newly isolated strains, morphologically identified as Chlamydomonas subg. Amphichloris, using 18S rRNA gene phylogeny, light microscopy, and mitochondria fluorescent microscopy. Molecular phylogenetic analyses revealed three independent lineages of the subgenus, separated from the type species of Chlamydomonas, Cd. reinhardtii. These three lineages were further distinguished from each other by light and fluorescent microscopy-in particular by the morphology of the papillae, chloroplast surface, stigmata, and mitochondria-and are here assigned to three genera: Dangeardinia emend., Ixipapillifera gen. nov., and Rhysamphichloris gen. nov. Based on the molecular and morphological data, two to three species were recognized in each genus, including one new species, I. pauromitos. In addition, Cd. deasonii, which was previously assigned to subgroup "Pleiochloris," was included in the genus Ixipapillifera as I. deasonii comb. nov.
  • Taxonomic revision of oil-producing green algae, Chlorococcum oleofaciens (Volvocales, Chlorophyceae), and its relatives.
    Yuriko Kawasaki; Takashi Nakada; Masaru Tomita
    Journal of phycology, 51, 5, 1000, 16, Oct. 2015, [International Magazine]
    English, Scientific journal, Historically, species in Volvocales were classified based primarily on morphology. Although the taxonomy of Chlamydomonas has been re-examined using a polyphasic approach including molecular phylogeny, that of Chlorococcum (Cc.), the largest coccoid genus in Volvocales, has yet to be reexamined. Six species thought to be synonymous with the oil-producing alga Cc. oleofaciens were previously not confirmed by molecular phylogeny. In this study, seven authentic strains of Cc. oleofaciens and its putative synonyms, along with 11 relatives, were examined based on the phylogeny of the 18S ribosomal RNA (rRNA) gene, comparisons of secondary structures of internal transcribed spacer 1 (ITS1) and ITS2 rDNA, and morphological observations by light microscopy. Seven 18S rRNA types were recognized among these strains and three were distantly related to Cc. oleofaciens. Comparisons of ITS rDNA structures suggested possible separation of the remaining four types into different species. Shapes of vegetative cells, thickness of the cell walls in old cultures, the size of cells in old cultures, and stigma morphology of zoospores also supported the 18S rRNA grouping. Based on these results, the 18 strains examined were reclassified into seven species. Among the putative synonyms, synonymy of Cc. oleofaciens, Cc. croceum, and Cc. granulosum was confirmed, and Cc. microstigmatum, Cc. rugosum, Cc. aquaticum, and Cc. nivale were distinguished from Cc. oleofaciens. Furthermore, another related strain is described as a new species, Macrochloris rubrioleum sp. nov.
  • New "missing link" genus of the colonial volvocine green algae gives insights into the evolution of oogamy
    Hisayoshi Nozaki; Toshihiro K. Yamada; Fumio Takahashi; Ryo Matsuzaki; Takashi Nakada
    BMC EVOLUTIONARY BIOLOGY, 14, 1, 37, Mar. 2014, [Peer-reviewed]
    English, Scientific journal
  • DESCRIPTION OF TWO NEW MONOECIOUS SPECIES OF VOLVOX SECT. VOLVOX (VOLVOCACEAE, CHLOROPHYCEAE), BASED ON COMPARATIVE MORPHOLOGY AND MOLECULAR PHYLOGENY OF CULTURED MATERIAL.
    Nanako Isaka; Hiroko Kawai-Toyooka; Ryo Matsuzaki; Takashi Nakada; Hisayoshi Nozaki
    Journal of phycology, 48, 3, 759, 67, Jun. 2012, [International Magazine]
    English, Scientific journal, Species of Volvox sect. Volvox (Volvocaceae, Chlorophyceae) are unique because they have thick cytoplasmic bridges between somatic cells and spiny-walled zygotes. This section is taxonomically important because the genus Volvox is polyphyletic. However, taxonomic studies of species in Volvox sect. Volvox have not been carried out on cultured material. Here, we performed a taxonomic study of monoecious species of Volvox sect. Volvox based on the comparative morphology and molecular phylogeny of chloroplast genes and the internal transcribed spacer (ITS) regions of nuclear rDNA using various strains originating from Japan and two preserved strains from the USA. The strains were clearly divided into four species, V. globator L., V. barberi W. Shaw, V. kirkiorum sp. nov., and V. ferrisii sp. nov., on the basis of differences in numbers of zygotes (eggs) in the sexual spheroids, form of zygote wall, and somatic cell shape. Sequences for ITS of nuclear rDNA resolved that the two new species have phylogenetic positions separated from V. globator, V. barberi, V. capensis F. Rich et Pocock, and V. rousseletii G. S. West UTEX 1862 within Volvox sect. Volvox.
  • EVOLUTIONARY ORIGIN OF GLOEOMONAS (VOLVOCALES, CHLOROPHYCEAE), BASED ON ULTRASTRUCTURE OF CHLOROPLASTS AND MOLECULAR PHYLOGENY
    Hisayoshi Nozaki; Takashi Nakada; Shin Watanabe
    JOURNAL OF PHYCOLOGY, 46, 1, 195, 200, Feb. 2010, [Peer-reviewed]
    English, Scientific journal
  • Recharacterization of Chlamydomonas reinhardtii and its relatives with new isolates from Japan.
    Takashi Nakada; Haruka Shinkawa; Takuro Ito; Masaru Tomita
    Journal of plant research, 123, 1, 67, 78, Jan. 2010, [Domestic magazines]
    English, Scientific journal, Chlamydomonas reinhardtii P. A. Dang. (Volvocales, Chlorophyceae) is one of the most intensely studied algae, and its whole genome was sequenced. Although this species was originally described based on materials from France and is often referred to as a cosmopolitan species, all culture strains available today have been isolated from eastern North America. The distinctions with similar and/or closely related species, such as Chlamydomonas globosa J. Snow and Chlamydomonas orbicularis E. G. Pringsh., are also contentious. In this study, new strains of C. reinhardtii and C. globosa were isolated from Japan and compared with several strains similar to C. reinhardtii. Based on the morphological, genealogical, phylogenetical, and mating studies including the new Japanese strains, the circumscription of C. reinhardtii was clarified. C. reinhardtii was most closely related to C. globosa, and they were shown to be different species. Although C. reinhardtii was similar to C. orbicularis, the authentic strain of C. orbicularis was morphologically distinguishable and phylogenetically distant from C. reinhardtii. Discovery of the Japanese strains of C. reinhardtii supports the cosmopolitan distribution of this species. Based on Japanese strains and/or strains from other countries, emended descriptions of C. reinhardtii, C. globosa, and C. orbicularis are given.
  • Another origin of coloniality in volvocaleans: the phylogenetic position of Pyrobotrys arnoldi (Spondylomoraceae, Volvocales).
    Takashi Nakada; Hisayoshi Nozaki; Masaru Tomita
    The Journal of eukaryotic microbiology, 57, 4, 379, 82, 2010, [International Magazine]
    English, Scientific journal, Colonial volvocaleans (Chlorophyceae) are used as a standard model of multicellular evolution. However, the phylogenetic position of the colonial volvocalean family Spondylomoraceae has yet to be resolved. To examine this, the molecular phylogenies of Pyrobotrys stellata and Pyrobotrys squarrosa were analyzed using combined 18S rRNA, RUBISCO large subunit, and P700 chl a-apoprotein A2 gene sequences. In the phylogenetic trees, Pyrobotrys belonged to the clade Caudivolvoxa and was not closely related to other colonial volvocalean flagellates. The results indicate that colony formation of Spondylomoraceae independently evolved from unicellular volvocaleans. The phylogenetic position of problematic "Pascherina tetras" SAG 159-1 was also analyzed.
  • TAXONOMIC STUDY OF TWO NEW GENERA OF FUSIFORM GREEN FLAGELLATES, TABRIS GEN. NOV. AND HAMAKKO GEN. NOV. (VOLVOCALES, CHLOROPHYCEAE).
    Takashi Nakada; Hisayoshi Nozaki
    Journal of phycology, 45, 2, 482, 92, Apr. 2009, [International Magazine]
    English, Scientific journal, On the basis of LM, we isolated strains of two species of fusiform green flagellates that could be assigned to former Chlorogonium (Cg.) Ehrenb. One species, "Cg."heimii Bourr., lacked a pyrenoid in its vegetative cells and required organic compounds for growth. The other was similar to Cg. elongatum (P. A. Dang.) Francé and "Cg."acus Nayal, but with slightly smaller vegetative cells. Their molecular phylogeny was also studied based on combined 18S rRNA, RUBISCO LSU (rbcL), and P700 chl a-apoprotein A2 (psaB) gene sequences. Both species were separated from Chlorogonium emend., Gungnir Nakada and Rusalka Nakada, which were formerly assigned to Chlorogonium. They were accordingly assigned to new genera, Tabris Nakada gen. nov. and Hamakko (Hk.) Nakada gen. nov. as T. heimii (Bourr.) Nakada comb. nov. and Hk. caudatus Nakada sp. nov., respectively. Tabris is differentiated from other genera of fusiform green flagellates by its vegetative cells, which only have two apical contractile vacuoles and lack a pyrenoid in the chloroplast. Hamakko, on the other hand, is distinguishable by the fact that its pyrenoids in vegetative cells are penetrated by flattened thylakoid lamellae.
  • Molecular systematics of Volvocales (Chlorophyceae, Chlorophyta) based on exhaustive 18S rRNA phylogenetic analyses (vol 48, pg 281, 2008)
    Takashi Nakada; Kazuharu Misawa; Hisayoshi Nozaki
    MOLECULAR PHYLOGENETICS AND EVOLUTION, 49, 2, 690, 690, Nov. 2008, [Peer-reviewed]
    English
  • Molecular systematics of Volvocales (Chlorophyceae, Chlorophyta) based on exhaustive 18S rRNA phylogenetic analyses.
    Takashi Nakada; Kazuharu Misawa; Hisayoshi Nozaki
    Molecular phylogenetics and evolution, 48, 1, 281, 91, Jul. 2008, [International Magazine]
    English, Scientific journal, The taxonomy of Volvocales (Chlorophyceae, Chlorophyta) was traditionally based solely on morphological characteristics. However, because recent molecular phylogeny largely contradicts the traditional subordinal and familial classifications, no classification system has yet been established that describes the subdivision of Volvocales in a manner consistent with the phylogenetic relationships. Towards development of a natural classification system at and above the generic level, identification and sorting of hundreds of sequences based on subjective phylogenetic definitions is a significant step. We constructed an 18S rRNA gene phylogeny based on 449 volvocalean sequences collected using exhaustive BLAST searches of the GenBank database. Many chimeric sequences, which can cause fallacious phylogenetic trees, were detected and excluded during data collection. The results revealed 21 strongly supported primary clades within phylogenetically redefined Volvocales. Phylogenetic classification following PhyloCode was proposed based on the presented 18S rRNA gene phylogeny along with the results of previous combined 18S and 26S rRNA and chloroplast multigene analyses.
  • MOLECULAR PHYLOGENY, ULTRASTRUCTURE, AND TAXONOMIC REVISION OF CHLOROGONIUM (CHLOROPHYTA): EMENDATION OF CHLOROGONIUM AND DESCRIPTION OF GUNGNIR GEN. NOV. AND RUSALKA GEN. NOV.
    Takashi Nakada; Hisayoshi Nozaki; Thomas Pröschold
    Journal of phycology, 44, 3, 751, 60, Jun. 2008, [International Magazine]
    English, Scientific journal, We examined the molecular phylogeny and ultrastructure of Chlorogonium and related species to establish the natural taxonomy at the generic level. Phylogenetic analyses of 18S rRNA and RUBISCO LSU (rbcL) gene sequences revealed two separate clades of Chlorogonium from which Chlorogonium (Cg.) fusiforme Matv. was robustly separated. One clade comprised Cg. neglectum Pascher and Cg. kasakii Nozaki, whereas the other clade included the type species Cg. euchlorum (Ehrenb.) Ehrenb., Cg. elongatum (P. A. Dang.) Francé, and Cg. capillatum Nozaki, M. Watanabe et Aizawa. On the basis of unique ultrastructural characteristics, we described Gungnir Nakada gen. nov. comprising three species: G. neglectum (Pascher) Nakada comb. nov., G. mantoniae (H. Ettl) Nakada comb. nov., and G. kasakii (Nozaki) Nakada comb. nov. We also emended Chlorogonium as a monophyletic genus composed of Cg. euchlorum, Cg. elongatum, and Cg. capillatum. Because Cg. fusiforme was distinguished from the redefined Chlorogonium and Gungnir by the structure of its starch plate, which is associated with pyrenoids, we reclassified this species as Rusalka fusiformis (Matv.) Nakada gen. et comb. nov.
  • Re-evaluation of three Chlorogonium (Volvocales, Chlorophyceae) species based on 18S ribosomal RNA gene phylogeny
    Takashi Nakada; Hisayoshi Nozaki
    EUROPEAN JOURNAL OF PHYCOLOGY, 42, 2, 177, 182, May 2007, [Peer-reviewed]
    English, Scientific journal
■ Other Activities and Achievements
■ Syllabus
  • 分類学概論, 2024年, 修士課程, 理学院
  • 多様性生物学特論Ⅱ, 2024年, 修士課程, 理学院
  • 多様性生物学研究法, 2024年, 修士課程, 理学院
  • 科学・技術の世界（1単位）, 2024年, 学士課程, 全学教育
  • 生物多様性概論, 2024年, 学士課程, 理学部
  • 環境と人間, 2024年, 学士課程, 全学教育
  • 多様性生物学Ⅰ, 2024年, 学士課程, 理学部
  • 臨海実習Ⅱ, 2024年, 学士課程, 理学部
  • ISP生物科学実習Ⅰ・a, 2024年, 学士課程, 理学部
  • ISP生物科学実習Ⅰ・b, 2024年, 学士課程, 理学部
  • 植物系統分類学実習, 2024年, 学士課程, 理学部
  • 植物系統分類学実習, 2024年, 学士課程, 総合教育部
  • 系統分類学b, 2024年, 学士課程, 理学部
  • 系統分類学b, 2024年, 学士課程, 理学部
  • 系統分類学Ⅱ, 2024年, 学士課程, 理学部
  • 系統分類学Ⅱ, 2024年, 学士課程, 理学部
  • 多様性生物学Ⅱ, 2024年, 学士課程, 理学部
  • 生物学Ⅱ, 2024年, 学士課程, 全学教育
■ Research Themes
  • ミクログレナ属藻類（緑藻綱）の分類学的見直しと好塩性・好冷性の系統進化
    科学研究費助成事業
    01 Apr. 2019 - 31 Mar. 2022
    仲田 崇志
    本研究では，単細胞性藻類の中でも，淡水から汽水・海氷に広く分布するミクログレナ属を対象に，藻類の生息可能環境や至適環境の実態とその進化過程の解明を目指した。
    2021年度には入手したミクログレナ属藻類7種の培養株について，淡水・汽水（1/5海水相当）・海水を模した培地中の，それぞれ15℃，20℃における増殖比較を進めた。期間終了時点では培地の色による定性的判断まで行い，固定試料を保存した。
    その結果，淡水由来の 6 株中 4 株は，いずれの温度でも淡水でのみ増殖し，汽水においては増殖が認められなかった。また 1 株は，いずれの温度でも淡水で最もよく増殖したが，汽水での増殖も認められ，海水では増殖しなかった。以上の5株においては，15℃よりも20℃でより速く増殖した。淡水産の残り 1 株は，15℃では海水において最もよく増殖し，次いで汽水でよく増殖したが，20℃においては汽水において最もよく増殖し，次いで淡水でやや増殖し，海水においてはほとんど増殖が認められなかった。またこの株は，同じ塩分濃度では20℃よりも15℃でより速く増殖した。海水由来の1株は，汽水・海水において増殖が認められ，特に20℃の海水において良好な増殖を示した。
    すなわち，培養株（種）によって至適温度・至適塩分濃度に差があり，また特定の種では至適塩分濃度が培養温度によって変化することが示された。この株は，系統的には海産系統から淡水系統への進化途上にある種と推定され，好冷性の種と近縁であった。
    今後，本研究で得られた固定試料を用いた細胞計数を進め，定量的なデータと共に英文論文として発表したい。
    また本研究の前提となる分類学的基礎研究として，「国際藻類・菌類・植物命名規約」の改訂に関して，Taxon誌2020年12月号に掲載された修正提案を紹介・解説するミニレビューが日本藻類学会和文誌「藻類」に受理・掲載された。
    日本学術振興会, 基盤研究(C), 横浜国立大学, 19K06813
  • Research on physiological differentiation among closely related unicellular green algae
    Grants-in-Aid for Scientific Research
    2010 - 2012
    NAKADA Takashi
    Several new strains of volvocalean algae, a major freshwater microalgal group, were established, and their morphological and phylogenetical properties were clarified. Three lineages including the new strains were selected and examined for the growth exami
    Japan Society for the Promotion of Science, Grant-in-Aid for Young Scientists (B), Keio University, 22770086
  • Biofuel creation by oil-producing microalgae ～Improvement method in lipid production of oil-producing microalgae by UVR～
    Grants-in-Aid for Scientific Research
    2010 - 2012
    OHI Nobuaki; NAKADA Takashi; ITO Takuro; SATO Dan
    Oceanic oil-producing microalgae has been focused for solution of global warming and energy problems. Microalgae are highly biofuel producer than plant biomass, no competition with food and growing ocean water. A part of microalgae accumulate oil by stress conditions and its oil-contents are variety by species. We had conducted screening of highly oil-producing marine microalgae and discovered potentiality strains as biofuel. We have developed the metabolomics and lipidomics analysis method for oceanic microalge to elucidate mechanisms of oil-accumulation by photooxidation stress to improve oil-production.
    Japan Society for the Promotion of Science, Grant-in-Aid for Scientific Research (C), 22612003