Directed Evolution of Ionizing Radiation Resistance in Escherichia coli
Directed Evolution of Ionizing Radiation Resistance in Escherichia coli
复制标题
DOI：
10.1128/jb.00502-09
复制
发表时间：
2009-08-15
影响因子：
3.2
通讯作者：
Battista, John R.
中科院分区：
文献类型：
--
作者：
Harris, Dennis R.;Pollock, Steve V.;Battista, John R.
通过定向进化，我们已经在一种相对敏感的细菌——大肠杆菌中产生了极端的电离辐射抗性。从MG1655菌株独立衍生出4个大肠杆菌K-12群体，每个群体都特别适应于暴露于高剂量电离辐射下的生存。从两个种群中分离出的菌株的D-37值接近耐辐射球菌所表现的值。对来自这些群体的9株纯化菌株进行了全基因组测序。观察到明确的突变模式，两者都指出了关键的潜在机制，并指导了菌株的进一步表征。在这些已进化的种群中，没有证据表明被动的基因组保护。相反，增强的重组DNA修复对基因组重组做出了突出但可能不是唯一的贡献。多基因、部分基因的多等位基因、多机制、多进化途径都在极端辐射抗性的进化获得中发挥作用。recA基因的几个突变和e14前噬菌体的缺失都明显有助于并部分解释这种新表型。细菌重组修复系统和复制重启前原体的其他成分的突变也很突出，参与细胞分裂、蛋白质周转和谷氨酸运输的基因的突变也很突出。至少一些极端抗辐射的进化途径受到特定等位基因在时间上有序出现的限制。
We have generated extreme ionizing radiation resistance in a relatively sensitive bacterial species, Escherichia coli, by directed evolution. Four populations of Escherichia coli K-12 were derived independently from strain MG1655, with each specifically adapted to survive exposure to high doses of ionizing radiation. D-37 values for strains isolated from two of the populations approached that exhibited by Deinococcus radiodurans. Complete genomic sequencing was carried out on nine purified strains derived from these populations. Clear mutational patterns were observed that both pointed to key underlying mechanisms and guided further characterization of the strains. In these evolved populations, passive genomic protection is not in evidence. Instead, enhanced recombinational DNA repair makes a prominent but probably not exclusive contribution to genome reconstitution. Multiple genes, multiple alleles of some genes, multiple mechanisms, and multiple evolutionary pathways all play a role in the evolutionary acquisition of extreme radiation resistance. Several mutations in the recA gene and a deletion of the e14 prophage both demonstrably contribute to and partially explain the new phenotype. Mutations in additional components of the bacterial recombinational repair system and the replication restart primosome are also prominent, as are mutations in genes involved in cell division, protein turnover, and glutamate transport. At least some evolutionary pathways to extreme radiation resistance are constrained by the temporally ordered appearance of specific alleles.