Antimicrobial Discovery Center, Department of Biology, Northeastern University, Boston, Massachusetts, USA.
mBio. 2022 Feb 22;13(1):e0342021. doi: 10.1128/mbio.03420-21. Epub 2022 Jan 4.
Persisters represent a small subpopulation of cells that are tolerant of killing by antibiotics and are implicated in the recalcitrance of chronic infections to antibiotic therapy. One general theme has emerged regarding persisters formed by different bacterial species, namely, a state of relative dormancy characterized by diminished activity of antibiotic targets. Within this framework, a number of studies have linked persister formation to stochastic decreases in energy-generating components, leading to low ATP and target activity. In this study, we screen knockouts in the main global regulators of Escherichia coli for their effect on persisters. A knockout in integration host factor (IHF) had elevated ATP and a diminished level of persisters. This was accompanied by an overexpression of isocitrate dehydrogenase (Icd) and a downregulation of isocitrate lyase (AceA), two genes located at the bifurcation between the tricarboxylic acid (TCA) cycle and the glyoxylate bypass. Using a translational fusion, we sort out rare bright cells, and this subpopulation is enriched in persisters. Our results suggest that noise in the expression of produces rare cells with low Icd/high AceA, diverting substrates into the glyoxylate bypass, which decreases ATP, leading to antibiotic-tolerant persisters. We further examine noise in a simple model, the operon, and show that a knockout of the repressor increases expression of the operon and decreases persister formation. Our results suggest that noise quenching by overexpression serves as a general approach to determine the nature of persister genes in a variety of bacterial species and conditions. Persisters are phenotypic variants that survive exposure to antibiotics through temporary dormancy. Mutants with increased levels of persisters have been identified in clinical isolates, and evidence suggests these cells contribute to chronic infections and antibiotic treatment failure. Understanding the underlying mechanism of persister formation and tolerance is important for developing therapeutic approaches to treat chronic infections. In this study, we examine a global regulator, IHF, that plays a role in persister formation. We find that noise in expression of IHF contributes to persister formation, likely by regulating the switch between the TCA cycle that efficiently produces energy and the glyoxylate bypass. We extend this study to a simple model operon and show that when grown on lactose as the sole carbon source, noise in its expression influences ATP levels and determines persister formation. This noise is quenched by overexpression of the operon, providing a simple approach to test the involvement of a gene in persister formation.
持久菌代表了一小部分对抗生素具有耐药性的细胞亚群,它们与慢性感染对抗生素治疗的顽固性有关。关于不同细菌种类形成的持久菌,有一个普遍的主题,即相对休眠状态,其特征是抗生素靶标活性降低。在这个框架内,许多研究将持久菌的形成与能量生成成分的随机减少联系起来,导致低 ATP 和靶标活性。在这项研究中,我们筛选了大肠杆菌主要全局调节剂的敲除体,以研究它们对持久菌的影响。整合宿主因子 (IHF) 的敲除导致 ATP 升高和持久菌水平降低。这伴随着异柠檬酸脱氢酶 (Icd) 的过表达和异柠檬酸裂合酶 (AceA) 的下调,AceA 是位于三羧酸 (TCA) 循环和乙醛酸旁路分叉处的两个基因。使用翻译融合,我们分离出罕见的亮细胞,这个亚群富含持久菌。我们的结果表明,产生低 Icd/高 AceA 的罕见细胞的表达存在噪声,将底物分流到乙醛酸旁路,从而降低 ATP,导致抗生素耐药性持久菌。我们进一步在一个简单的模型,即 操纵子中检查噪声,并表明 阻遏物的敲除增加了操纵子的表达并减少了持久菌的形成。我们的结果表明,过表达的噪声猝灭可作为一种通用方法来确定各种细菌种类和条件下持久菌基因的性质。持久菌是表型变体,通过暂时休眠来耐受抗生素。在临床分离株中已经鉴定出具有更高水平持久菌的突变体,并且有证据表明这些细胞有助于慢性感染和抗生素治疗失败。了解持久菌形成和耐受性的潜在机制对于开发治疗慢性感染的治疗方法很重要。在这项研究中,我们研究了一种全局调节剂 IHF,它在持久菌形成中起作用。我们发现 IHF 表达的噪声有助于持久菌的形成,这可能是通过调节 TCA 循环与乙醛酸旁路之间的转换来实现的,TCA 循环有效地产生能量,而乙醛酸旁路则产生能量。我们将这项研究扩展到一个简单的模型 操纵子,并表明当以乳糖作为唯一碳源生长时,其表达的噪声会影响 ATP 水平并决定持久菌的形成。该噪声通过 操纵子的过表达而猝灭,为测试基因在持久菌形成中的参与提供了一种简单的方法。