Ecology and physiology of anaerobic protists in marine sediments

2019 Fiscal Year Final Research Report

• Project/Area Number: 16K07828
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Research Field: Aquatic bioproduction science
• Research Institution: Fukui Prefectural University
• Principal Investigator: Kondo Ryuji 福井県立大学, 海洋生物資源学部, 教授 (30244528)
• Co-Investigator(Kenkyū-buntansha): 高尾 祥丈 福井県立大学, 海洋生物資源学部, 准教授 (00511304)
• Project Period (FY): 2016-04-01 – 2020-03-31
• Keywords: 嫌気 / 底泥 / 鞭毛虫 / 原生生物 / 現存量 / 多様性

Outline of Final Research Achievements

Abundance and community composition of benthic heterotrophic nanoflagellates (HNF) were investigated in the surface layer of anoxic bottom sediment in the saline Lake Hiruga, Fukui, Japan. HNF cells were recovered from the sediment samples by Percoll density gradient centrifugation and were counted by epifluorescence microscopy. The HNF abundance in the anoxic sediment was 10- to 100-fold higher than that in oxic water column of the lake. Sequences of the V4-V5 hypervariable region of 18S rRNA genes were analysed using high throughput sequencing (HTS). Application of an HTS technique indicated immense protist diversity and potentially novel phyla in anoxic sediments of the lake. Our comprehensive analyses of HNF abundance and diversity provide a blueprint for the further understanding of ecological roles of HNF in anoxic sediment microbial food web.

Free Research Field

微生物生態学

Academic Significance and Societal Importance of the Research Achievements

水圏の嫌気的な底泥中の微生物の現存量や多様性については、原核微生物については多くの研究がなされてきたが、真核微生物に関する研究は殆どなかった。硫化水素が多量に蓄積するような嫌気的な環境でも、高い現存量で鞭毛虫が存在し、その多様性が極めて高いことが、本研究で明らかとなった。嫌気的な底泥では、発酵細菌や硫酸還元菌などの嫌気性細菌がその役割を分担しながら有機物分解を担っているとされてきたが、細菌摂食を行う多様な原生生物が多量に存在することが明らかになったことは、嫌気環境での有機物の分解過程や物質循環過程を再考する機会を与え、その学術的意義は大きいと考えられる。