Natural Escherichia coli isolates rapidly acquire genetic changes upon laboratory domestication
Natural Escherichia coli isolates rapidly acquire genetic changes upon laboratory domestication
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天然大肠杆菌分离株在实验室驯化后迅速发生遗传变化
DOI：
10.1099/mic.0.000405
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发表时间：
2017-01-01
期刊：
影响因子：
2.8
通讯作者：
Ferenci, Thomas
中科院分区：
文献类型：
--
作者：
Liu, Bin;Eydallin, Gustavo;Ferenci, Thomas
通过对从其自然栖息地中新分离的属于不同分类群的4株大肠杆菌的基因组变化的探索，分析了环境细菌对实验室条件的适应性。在自然分离株的所有培养物中，在富媒体中转移的10天内或在涉及延长的静止期的单个生长周期内，存在多达25个突变。在众多的个体突变中，两个基因在不同的背景下平行受到影响。Rpos(编码西格玛因子rpos)突变改变了大肠杆菌中的增殖和生存权衡，在来自所有四个不同祖先的分离株中都存在。更令人惊讶的是，两个不同的自然分离株获得了mut L突变，影响了DNA错配修复，第三个分离株也涉及更高的突变率。这些分离株的突变率升高表明，实验室驯化导致遗传不稳定性增加的危险。在已经驯化的MG1655实验室菌株中既没有检测到rpos突变，也没有检测到突变；在相同的培养条件下，实验室菌株中只有一个新的突变或没有新的突变。我们的结果表明，它能迅速适应实验室环境。在实验室中也会出现祖先特有的反应，突变事件对培养条件也很敏感，例如延长的固定期。为了保持自然菌株的稳定状态，我们的数据表明，菌株向实验室的过渡应该最大限度地减少培养周期和延长静止期。
The adaptation of environmental bacteria to laboratory conditions was analysed through the exploration of genomic changes in four strains of Escherichia coli freshly isolated from their natural habitats and belonging to different taxonomic clusters. Up to 25 mutations were present in all cultures of natural isolates within 10 days of transfer in rich media or with a single growth cycle involving an extended stationary phase. Among numerous individual mutations, two genes were affected in parallel in distinct backgrounds. Mutations in rpoS (encoding sigma factor RpoS), altering a multiplication-survival trade-off in E. coli, were present in isolates derived from all four different ancestors. More surprisingly, two different natural isolates acquired mutations in mutL, affecting DNA mismatch repair, and a third also involved higher mutation rates. The elevated mutation rates in these isolates indicate the danger of increased genetic instability arising from laboratory domestication. Neither rpoS nor mutator mutations were detected in the already-acclimatized MG1655 laboratory strain; only one or no new mutations were present in the laboratory strain under the same culture conditions. Our results indicate rapid adaptation to the laboratory environment. Ancestor-specific responses also arise in the laboratory and mutational events are also sensitive to culture conditions such as extended stationary phase. To maintain natural isolates in a stable state, our data suggest that the transition of strains to the laboratory should minimize culture cycles and extended stationary phase.