Department of Chemical and Biological Engineering, Princeton University, Princeton, NJ 08544.
Department of Chemical and Biological Engineering, Princeton University, Princeton, NJ 08544
Proc Natl Acad Sci U S A. 2018 Jul 3;115(27):E6301-E6309. doi: 10.1073/pnas.1804218115. Epub 2018 Jun 18.
Bacterial persisters are subpopulations of phenotypic variants in isogenic cultures that can survive lethal doses of antibiotics. Their tolerances are often attributed to reduced activities of antibiotic targets, which limit corruption and damage in persisters compared with bacteria that die from treatment. However, that model does not hold for nongrowing populations treated with ofloxacin, a fluoroquinolone, where antibiotic-induced damage is comparable between cells that live and those that die. To understand how those persisters achieve this feat, we employed a genetic system that uses orthogonal control of MazF and MazE, a toxin and its cognate antitoxin, to generate model persisters that are uniformly tolerant to ofloxacin. Despite this complete tolerance, MazF model persisters required the same DNA repair machinery (RecA, RecB, and SOS induction) to survive ofloxacin treatment as their nongrowing, WT counterparts and exhibited similar indicators of DNA damage from treatment. Further investigation revealed that, following treatment, the timing of DNA repair was critical to MazF persister survival because, when repair was delayed until after growth and DNA synthesis resumed, survival was compromised. In addition, we found that, with nongrowing, WT planktonic and biofilm populations, stalling the resumption of growth and DNA synthesis after the conclusion of fluoroquinolone treatment with a prevalent type of stress at infection sites (nutrient limitation) led to near complete survival. These findings illustrate that the timing of events, such as DNA repair, following fluoroquinolone treatment is important to persister survival and provide further evidence that knowledge of the postantibiotic recovery period is critical to understanding persistence phenotypes.
细菌持久型是同基因培养物中表型变异的亚群，能够在致死剂量的抗生素下存活。它们的耐受性通常归因于抗生素靶标的活性降低，与因治疗而死亡的细菌相比，这些靶标限制了持久型细菌的腐败和损伤。然而，对于用氟喹诺酮类药物氧氟沙星治疗的非生长群体，该模型并不适用，因为在活细胞和死亡细胞之间，抗生素诱导的损伤相当。为了了解这些持久型如何实现这一壮举，我们采用了一种遗传系统，该系统使用正交控制 MazF 和 MazE（一种毒素及其同源解毒剂）来产生对氧氟沙星具有均匀耐受性的模型持久型。尽管具有这种完全的耐受性，但 MazF 模型持久型在接受氧氟沙星治疗时需要相同的 DNA 修复机制（RecA、RecB 和 SOS 诱导）来存活，就像它们的非生长、WT 对应物一样，并且表现出相似的治疗引起的 DNA 损伤指标。进一步的研究表明，治疗后，DNA 修复的时机对 MazF 持久型的存活至关重要，因为当修复延迟到生长和 DNA 合成恢复后进行时，生存能力就会受到影响。此外，我们发现，对于非生长的、WT 的浮游生物和生物膜群体，在用感染部位常见的应激物质（营养限制）来阻止氟喹诺酮治疗后生长和 DNA 合成的恢复，几乎可以完全存活。这些发现表明，在氟喹诺酮治疗后，如 DNA 修复等事件的时间安排对持久型的存活很重要，并进一步证明，了解抗生素后恢复期间的知识对于理解持久性表型至关重要。
