Posibilty of sympatric speciation of protists by cellular symbiosis

2018 Fiscal Year Final Research Report

• Project/Area Number: 17K19423
• Research Category: Grant-in-Aid for Challenging Research (Exploratory)
• Allocation Type: Multi-year Fund
• Research Field: Ecology and Evolution (including anthropology), and related fields
• Research Institution: Tokyo Institute of Technology
• Principal Investigator: Hongoh Yuichi 東京工業大学, 生命理工学院, 教授 (90392117)
• Co-Investigator(Kenkyū-buntansha): 木原 久美子 熊本高等専門学校, 生物化学システム工学科, 准教授 (50622916)
• Research Collaborator: Fukuda Shinji 慶応大学, 政策メディア研究科, 特任教授 ; Sakai Miho 東京工業大学, 生命理工学院, 大学院生
• Project Period (FY): 2017-06-30 – 2019-03-31
• Keywords: 共生 / 種分化 / 原生生物 / 腸内微生物 / メタン菌

Outline of Final Research Achievements

This study aimed to test my hypothesis that single-celled eukaryotes (protists) can speciate by acquiring symbiotic prokaryotes. For this purpose, I selected a termite-gut protist genus as the material to be examined. Although the protist genus has been regarded monospecific, I demonstrated that it comprises two distinct species and that the two species can be discriminated by the presence or absence of endosymbiotic archaea. The genome analysis of the symbiotic archaeon indicated that the genome is very similar to its free-living relatives; the symbiosis has emerged relatively recently. Thus, this study strongly suggests that cellular symbiosis with prokaryotes can lead to speciation of a protist, though further studies are needed to prove this.

Free Research Field

分子生態学

Academic Significance and Societal Importance of the Research Achievements

生物の「種」がどのように形成されたか、というのは生物学上の重要なテーマである。本研究課題では、新たな種分化過程の仮説を提唱し、該当する可能性のある事例を材料として検証した。その結果、単細胞真核生物である原生生物の場合、細胞内に原核生物（細菌と古細菌）が共生することで種分化を引き起こす可能性が強く示唆された。これは、多様な原生生物種の存在を（部分的に）説明する、進化学上の重要な成果である。