病原性Escherichia coliにおける毒性の並列進化

S D Reid¹, C J Herbelin, A C Bumbaugh

¹Institute of Molecular Evolutionary Genetics, Pennsylvania State University, University Park 16802, USA.

Nature

|July 14, 2000

まとめ

E. coli O157:H7を含む病原性Escherichia coliの進化は,数百万年前に始まった. 自然選択は,毒性の遺伝子の秩序ある獲得を好み,病原体の脅威を増加させた.

科学分野:

微生物学微生物学とは
進化生物学の進化生物学について
遺伝学遺伝学とは

背景:

新しい細菌病原体に繋がる進化の経路は,ほとんど不明のままである.
病原性エシェリキア大腸菌 (E. coli) の出現を理解することは,公衆衛生にとって極めて重要です.

研究の目的:

病原性E. coli菌株における進化史とウイルス性遺伝子獲得を解明する.
E. coli の病原体進化の系統遺伝的関係と時間軸を再構築する.

主な方法:

系統遺伝子の樹を構成するために7つの家政遺伝子の配列を解析する.
再結合が系統遺伝信号に与える影響を評価するための互換性分析.
E. coli と Salmonella enterica. の同名置換率を用いた分岐時間の推定.

主要な成果:

系統遺伝学的分析は,再結合が祖先の染色体信号を完全に遮断していないことを明らかにしました.
大腸菌クローンの放射は,およそ900万年前に始まった.
非常に毒性の高いE. coli O157:H7は,E. coli K-12の祖先から約450万年前に分離した.
古いE. coliの系統は,病原性島,ヘモリシン,シガ毒素などの同一の毒性因子を独立して獲得した.

結論:

毒性の要因の並列進化は,病原性E. coliにおける強い選択的圧力を示唆している.
自然淘汰は遺伝子の有序な獲得を促し,バクテリアの毒性を徐々に高めています.
この研究は,E. coliの病原性メカニズムの段階的な発達についての洞察を提供します.

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