The SOS response increases bacterial fitness, but not evolvability, under a sublethal dose of antibiotic

Exposure to antibiotics induces the expression of mutagenic bacterial stress–response pathways, but the evolutionary benefits of these responses remain unclear. One possibility is that stress–response pathways provide a short-term advantage by protecting bacteria against the toxic effects of antibiotics. Second, it is possible that stress-induced mutagenesis provides a long-term advantage by accelerating the evolution of resistance. Here, we directly measure the contribution of the Pseudomonas aeruginosa SOS pathway to bacterial fitness and evolvability in the presence of sublethal doses of ciprofloxacin. Using short-term competition experiments, we demonstrate that the SOS pathway increases competitive fitness in the presence of ciprofloxacin. Continued exposure to ciprofloxacin results in the rapid evolution of increased fitness and antibiotic resistance, but we find no evidence that SOS-induced mutagenesis accelerates the rate of adaptation to ciprofloxacin during a 200 generation se...

抗生素暴露可诱导致突变性细菌应激应答通路（mutagenic bacterial stress-response pathways）的表达，但此类应答的进化益处仍未明确。一种可能性是，应激应答通路可通过保护细菌抵御抗生素的毒性作用，为其带来短期生存优势；另一种可能则是，应激诱导突变（stress-induced mutagenesis）可通过加速耐药性的进化，为细菌提供长期进化优势。本研究直接测定了铜绿假单胞菌（Pseudomonas aeruginosa）的SOS应答通路（SOS pathway）在亚致死剂量环丙沙星（ciprofloxacin）存在的条件下，对细菌适合度及进化能力的贡献。通过短期竞争实验，我们证实：在环丙沙星存在时，SOS通路可提升细菌的竞争适合度。持续暴露于环丙沙星会导致细菌适合度与抗生素耐药性快速进化，但我们未发现证据表明，在200代的传代培养过程中，SOS诱导的突变加速了细菌对环丙沙星的适应性进化速率……