Department of Veterinary and Biomedical Sciences, College of Veterinary Medicine, University of Minnesota, Saint Paul, MN, USA.
Department of Food and Bioproduct Sciences, University of Saskatchewan, Saskatoon, Canada.
Proteomics. 2018 Feb;18(3-4). doi: 10.1002/pmic.201700285. Epub 2018 Jan 25.
The emergence of multidrug resistance in bacteria has reached alarming levels. To solve this growing problem, discovery of novel cellular targets or pathways important for antimicrobial resistance is urgently needed. In this study, we explored how the alternative sigma factor, RpoE, protects Escherichia coli O157 against the toxic effects of the polycationic antimicrobial agent, chlorhexidine (CHX). Susceptibility of this organism to CHX was found to directly correlate to the growth rate, with the faster replicating wild-type being more susceptible to CHX than its more slowly replicating ΔrpoE O157 mutant. Once the wild-type and rpoE mutant strains had undergone growth arrest (entered the stationary growth phase), their resistance to CHX became entirely dependent on the functionality of RpoE. The RpoE regulon plays a critical role in maintaining the integrity of the asymmetric lipid bilayer of E. coli, thereby preventing the intracellular accumulation of CHX. Finally, using a single-cell, high-resolution, synchrotron-based approach, we discovered a subpopulation of the rpoE mutant strain with no detectable intracellular CHX, a predominant characteristic of the wild-type CHX-resistant population. This finding reveals a role of phenotypic heterogeneity in antimicrobial resistance.
细菌的多药耐药性的出现已经达到了惊人的水平。为了解决这个日益严重的问题，迫切需要发现对抗微生物耐药性很重要的新型细胞靶标或途径。在这项研究中，我们探讨了替代 sigma 因子 RpoE 如何保护大肠杆菌 O157 免受多阳离子抗菌剂洗必泰（CHX）的毒性影响。该生物体对 CHX 的敏感性与生长速度直接相关，快速复制的野生型比其复制速度较慢的 rpoE 缺失突变体 O157 更容易受到 CHX 的影响。一旦野生型和 rpoE 突变菌株停止生长（进入静止生长阶段），它们对 CHX 的抗性完全取决于 RpoE 的功能。RpoE 调控子在维持大肠杆菌不对称脂质双层的完整性方面起着关键作用，从而防止 CHX 在细胞内积累。最后，我们使用基于同步加速器的单细胞、高分辨率方法发现，rpoE 突变株的一个亚群中没有检测到细胞内 CHX，这是野生型 CHX 抗性群体的主要特征。这一发现揭示了表型异质性在抗微生物耐药性中的作用。
