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【文献】用于进化实验的点突变率可调的大肠杆菌

突变率和突变对适应度的影响对进化至关重要。由于突变率修饰因子和突变对适合度的影响之间的联系，突变率正在选择中。较高突变率和更有益突变之间的联系选择较高突变率，而较高突变率和更有害突变之间的联系选择较低突变率。突变率选择的净方向取决于适应度景观，大量的工作已经阐明了突变的适应度景观。然而，测试在单一环境中改变单一生物的突变率对进化的影响一直很困难。已经使用抗突变株和突变株研究了这一点，但这些菌株可能在其他方面有所不同，并且通常不允许突变率的连续变化。为了帮助研究突变率对进化的影响，我们通过基因工程改造了一种大肠杆菌菌株，其点突变率可以在两个数量级内平滑变化。我们通过改造错配修复蛋白MutH和MutL的可诱导控制菌株来实现这一目标。我们在大约350代的进化实验中使用了这种菌株，控制了突变率的变化。我们证实了构建体和突变率在这段时间内是稳定的。对进化菌株的测序显示，在较高的突变率下，单核苷酸多态性的数量较高，这可能是由于这些突变的有益影响或它们与有益突变的联系。

The mutation rate and mutations' effects on fitness are crucial to evolution. Mutation rates are under selection due to linkage between mutation rate modifiers and mutations' effects on fitness. The linkage between a higher mutation rate and more beneficial mutations selects for higher mutation rates, while the linkage between a higher mutation rate and more deleterious mutations selects for lower mutation rates. The net direction of selection on mutations rates depends on the fitness landscape, and a great deal of work has elucidated the fitness landscapes of mutations. However, tests of the effect of varying a mutation rate on evolution in a single organism in a single environment have been difficult. This has been studied using strains of antimutators and mutators, but these strains may differ in additional ways and typically do not allow for continuous variation of the mutation rate. To help investigate the effects of the mutation rate on evolution, we have genetically engineered a strain of Escherichia coli with a point mutation rate that can be smoothly varied over two orders of magnitude. We did this by engineering a strain with inducible control of the mismatch repair proteins MutH and MutL. We used this strain in an approximately 350 generation evolution experiment with controlled variation of the mutation rate. We confirmed the construct and the mutation rate were stable over this time. Sequencing evolved strains revealed a higher number of single nucleotide polymorphisms at higher mutations rates, likely due to either the beneficial effects of these mutations or their linkage to beneficial mutations.

Escherichia coli with a Tunable Point Mutation Rate for Evolution Experiments - PubMed (nih.gov)