Studies on genetic and physiological change of a bloom-forming cyanobacterium through interaction with its phages

2016 Fiscal Year Final Research Report

• Project/Area Number: 26281031
• Research Category: Grant-in-Aid for Scientific Research (B)
• Allocation Type: Partial Multi-year Fund
• Section: 一般
• Research Field: Environmental impact assessment
• Research Institution: Kyoto University
• Principal Investigator: Yoshida Takashi 京都大学, (連合)農学研究科(研究院), 准教授 (80305490)
• Co-Investigator(Kenkyū-buntansha): 左子 芳彦 京都大学, (連合)農学研究科(研究院), 教授 (60153970) ; 金子 貴一 京都産業大学, 公私立大学の部局等, 教授 (80370922)
• Project Period (FY): 2014-04-01 – 2017-03-31
• Keywords: バクテリオファージ / ラン藻 / ミクロキスティス / 共進化

Outline of Final Research Achievements

The cyanobacterium Microcystis frequently forms massive blooms in global freshwaters. Our previous genomic analyses on CRISPR arrays, which a marker for viral infection history, suggest that Microcystis and phage have co-evolved based on a frequency-dependent selection. The aim of this study is to understand co-evolutionary dynamics of Microcystis and phage in natural settings. In this field study, a CRISPR-related genotype (CT19) occupied in a Microcystis bloom and the CT19 consisted of the two major variants. These major CTs co-existed and oscillated throughout the sampling periods. Meanwhile few variations, which is derived from the acquisition of new spacers or the lack of spacers at the leader-end of the major variants, were observed. These indicate that Microcystis and phage co-evolution not only creates new genetic variations but also maintains their genetic diversity in a bloom. Further a growth experiment suggested that genetic change basically lessened host fitness.

Free Research Field

水圏微生物学