Biochemistry and Molecular Biophysics Graduate Group, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, Pennsylvania, USA; Department of Medicine, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, Pennsylvania, USA; Department of Biochemistry and Biophysics, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, Pennsylvania, USA.
Department of Medicine, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, Pennsylvania, USA.
mSphere. 2016 Aug 10;1(4). doi: 10.1128/mSphere.00163-16. eCollection 2016 Jul-Aug.
The bacterial SOS response is a DNA damage repair network that is strongly implicated in both survival and acquired drug resistance under antimicrobial stress. The two SOS regulators, LexA and RecA, have therefore emerged as potential targets for adjuvant therapies aimed at combating resistance, although many open questions remain. For example, it is not well understood whether SOS hyperactivation is a viable therapeutic approach or whether LexA or RecA is a better target. Furthermore, it is important to determine which antimicrobials could serve as the best treatment partners with SOS-targeting adjuvants. Here we derived Escherichia coli strains that have mutations in either lexA or recA genes in order to cover the full spectrum of possible SOS activity levels. We then systematically analyzed a wide range of antimicrobials by comparing the mean inhibitory concentrations (MICs) and induced mutation rates for each drug-strain combination. We first show that significant changes in MICs are largely confined to DNA-damaging antibiotics, with strains containing a constitutively repressed SOS response impacted to a greater extent than hyperactivated strains. Second, antibiotic-induced mutation rates were suppressed when SOS activity was reduced, and this trend was observed across a wider spectrum of antibiotics. Finally, perturbing either LexA or RecA proved to be equally viable strategies for targeting the SOS response. Our work provides support for multiple adjuvant strategies, while also suggesting that the combination of an SOS inhibitor with a DNA-damaging antibiotic could offer the best potential for lowering MICs and decreasing acquired drug resistance. IMPORTANCE Our antibiotic arsenal is becoming depleted, in part, because bacteria have the ability to rapidly adapt and acquire resistance to our best agents. The SOS pathway, a widely conserved DNA damage stress response in bacteria, is activated by many antibiotics and has been shown to play central role in promoting survival and the evolution of resistance under antibiotic stress. As a result, targeting the SOS response has been proposed as an adjuvant strategy to revitalize our current antibiotic arsenal. However, the optimal molecular targets and partner antibiotics for such an approach remain unclear. In this study, focusing on the two key regulators of the SOS response, LexA and RecA, we provide the first comprehensive assessment of how to target the SOS response in order to increase bacterial susceptibility and reduce mutagenesis under antibiotic treatment.
细菌 SOS 反应是一种 DNA 损伤修复网络，强烈暗示在抗菌应激下的存活和获得性药物耐药性。两个 SOS 调节剂 LexA 和 RecA 因此成为针对抗药性的辅助治疗的潜在目标，尽管仍有许多悬而未决的问题。例如，尚不清楚 SOS 过度激活是否是一种可行的治疗方法，或者 LexA 或 RecA 是更好的目标。此外，确定哪些抗菌药物可以作为与 SOS 靶向佐剂的最佳治疗伙伴非常重要。在这里，我们构建了大肠杆菌菌株，这些菌株在 lexA 或 recA 基因中具有突变，以涵盖可能的 SOS 活性水平的全谱。然后，我们通过比较每种药物-菌株组合的平均抑制浓度（MIC）和诱导突变率，系统地分析了广泛的抗菌药物。我们首先表明，MIC 的显著变化主要局限于 DNA 损伤抗生素，具有组成型受抑制 SOS 反应的菌株受到的影响比高活性菌株更大。其次，当 SOS 活性降低时，抗生素诱导的突变率受到抑制，这种趋势在更广泛的抗生素范围内观察到。最后，干扰 LexA 或 RecA 被证明是针对 SOS 反应的同样可行的策略。我们的工作为多种辅助策略提供了支持，同时也表明 SOS 抑制剂与 DNA 损伤抗生素的组合可能为降低 MIC 和减少获得性药物耐药性提供最佳潜力。
重要性
我们的抗生素武器库正在枯竭，部分原因是细菌具有快速适应和获得对我们最佳药物的耐药性的能力。SOS 途径是细菌中广泛保守的 DNA 损伤应激反应，许多抗生素都会激活该途径，并已被证明在促进抗生素应激下的存活和耐药性进化方面发挥着核心作用。因此，靶向 SOS 反应已被提议作为一种辅助策略来重振我们现有的抗生素武器库。然而，这种方法的最佳分子靶标和伙伴抗生素仍然不清楚。在这项研究中，我们专注于 SOS 反应的两个关键调节剂 LexA 和 RecA，首次全面评估了如何靶向 SOS 反应，以增加细菌对药物的敏感性并减少抗生素治疗下的突变。
