Data from: A trade-off between oxidative stress resistance and DNA repair plays a role in the evolution of elevated mutation rates in bacteria

The dominant paradigm for the evolution of mutator alleles in bacterial populations is that they spread by indirect selection for linked beneficial mutations when bacteria are poorly adapted. In this paper, we challenge the ubiquity of this paradigm by demonstrating that a clinically important stressor, hydrogen peroxide, generates direct selection for an elevated mutation rate in the pathogenic bacterium Pseudomonas aeruginosa as a consequence of a trade-off between the fidelity of DNA repair and hydrogen peroxide resistance. We demonstrate that the biochemical mechanism underlying this trade-off in the case of mutS is the elevated secretion of catalase by the mutator strain. Our results provide the first experimental evidence that direct selection can favour mutator alleles in bacterial populations, and pave the way for future studies to understand how mutation and DNA repair are linked to stress responses and how this impacts the evolution of bacterial mutation rates.

细菌种群中增变等位基因（mutator allele）演化的主流范式认为：当细菌适应性欠佳时，此类等位基因通过对连锁有益突变的间接选择实现扩散。本研究对该范式的普适性提出挑战，证实临床相关的重要胁迫因子过氧化氢（hydrogen peroxide）会对致病性细菌铜绿假单胞菌（Pseudomonas aeruginosa）的高突变率产生直接选择压力，该现象源于DNA修复（DNA repair）保真度与过氧化氢抗性之间的权衡关系。本研究进一步证实，在mutS增变基因的相关案例中，该权衡关系的生化机制为增变菌株的过氧化氢酶（catalase）分泌量升高。本研究结果首次通过实验证明，直接选择可在细菌种群中青睐增变等位基因，同时为后续研究厘清突变与DNA修复如何与胁迫应答相关联、以及该关联如何影响细菌突变率的演化铺平了道路。