2021 Fiscal Year Final Research Report
Genetic study on bacterial colony formation and its application to isolation of bacteria
| Project/Area Number |
17H03789
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Applied microbiology
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| Research Institution | Tokyo University of Agriculture (2020-2021)
The University of Tokyo (2017-2019) |
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Principal Investigator |
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| Co-Investigator(Kenkyū-buntansha) |
清水 則夫 東京医科歯科大学, 統合研究機構, 准教授 (30226245)
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| Project Period (FY) |
2017-04-01 – 2021-03-31
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| Keywords | 大腸菌 / コロニー形成 / 温度感受性変異 / MPN法 / 液体培養 / 不飽和脂肪酸 / cAMP / VBNC |
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| Outline of Final Research Achievements |
Most of bacteria in nature do not form colonies on solid media. To know its genetic background, we isolated Escherichia coli mutants that hardly form colonies compared to liquid cultivation. Characterization of the mutants revealed the importance of unsaturated fatty acids in colony formation. When faced with starvation, even wild-type E. coli falls in shortage of fatty acids, causing decrease of colony formation. When fatty acid synthesis was inhibited with chemical drugs, colony formation was impaired in not only E. coli but also Bacillus subtilis, Staphylococcal epidermidis and Corynebacterium glutamicum, suggesting its generality in bacteria.
In the course of screening of essential genes for the maintenance of colony-forming activity of E. coli in the viable but non-culturable state, we found that both cyaA- and & crp- strains keep high colony-forming activities for a long time, suggesting that cAMP-CRP is a global switch to lead cells to dormancy on starvation stress.
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| Free Research Field |
微生物学，分子生物学
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| Academic Significance and Societal Importance of the Research Achievements |
伝統的に細菌が生きている証拠とされてきたコロニー形成を相対化し，コロニーを作れない変異体を分離することで，コロニー形成が特殊な生物現象であることを示した。その変異を糸口にして，飢餓に接した細菌がコロニー形成能を落とす隠れた一因が，栄養要求性とは異なる不飽和脂肪酸の欠乏にあることを見出し，その供給が一般細菌の分離にも重要であることを示唆した。
飢餓に曝された大腸菌がコロニーを作らなくなるVBNC現象を，細胞増殖能の減衰という一面だけでなく， cAMPをシグナルとして増殖能を積極的に遮断して休眠状態に入っていく過程である可能性を示した。
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