Byrne Rose T, Klingele Audrey J, Cabot Eric L, Schackwitz Wendy S, Martin Jeffrey A, Martin Joel, Wang Zhong, Wood Elizabeth A, Pennacchio Christa, Pennacchio Len A, Perna Nicole T, Battista John R, Cox Michael M
Department of Biochemistry, University of Wisconsin-Madison, Madison, United States.
Elife. 2014 Mar 4;3:e01322. doi: 10.7554/eLife.01322.
By directed evolution in the laboratory, we previously generated populations of Escherichia coli that exhibit a complex new phenotype, extreme resistance to ionizing radiation (IR). The molecular basis of this extremophile phenotype, involving strain isolates with a 3-4 order of magnitude increase in IR resistance at 3000 Gy, is now addressed. Of 69 mutations identified in one of our most highly adapted isolates, functional experiments demonstrate that the IR resistance phenotype is almost entirely accounted for by only three of these nucleotide changes, in the DNA metabolism genes recA, dnaB, and yfjK. Four additional genetic changes make small but measurable contributions. Whereas multiple contributions to IR resistance are evident in this study, our results highlight a particular adaptation mechanism not adequately considered in studies to date: Genetic innovations involving pre-existing DNA repair functions can play a predominant role in the acquisition of an IR resistance phenotype. DOI: http://dx.doi.org/10.7554/eLife.01322.001.
通过在实验室中进行定向进化，我们之前培育出了具有复杂新表型的大肠杆菌群体，即对电离辐射（IR）具有极强的抗性。现在我们来探讨这种嗜极端菌表型的分子基础，该表型涉及在3000戈瑞剂量下对IR抗性增加3 - 4个数量级的菌株分离物。在我们适应性最强的一个分离株中鉴定出的69个突变中，功能实验表明，IR抗性表型几乎完全由DNA代谢基因recA、dnaB和yfjK中的仅三个核苷酸变化所导致。另外四个基因变化也有微小但可测量的贡献。尽管在本研究中对IR抗性有多种贡献，但我们的结果突出了一种迄今研究中未充分考虑的特殊适应机制：涉及预先存在的DNA修复功能的基因创新在获得IR抗性表型中可发挥主要作用。DOI: http://dx.doi.org/10.7554/eLife.01322.001 。
