The Institute for Drug Research, The Hebrew University of Jerusalemgrid.9619.7, Jerusalem, Israel.
Department of Microbiology and Molecular Genetics, Institute of Medical Research Israel-Canada, Faculty of Medicine, The Hebrew University of Jerusalemgrid.9619.7, Jerusalem, Israel.
mSystems. 2022 Jun 28;7(3):e0020222. doi: 10.1128/msystems.00202-22. Epub 2022 Apr 28.
The cell envelope of Gram-negative bacteria is a complex structure, essential for bacterial survival and for resistance to many antibiotics. Channels that cross the bacterial envelope and the host cell membrane form secretion systems that are activated upon attachment to host, enabling bacteria to inject effector molecules into the host cell, required for bacterium-host interaction. The type III secretion system (T3SS) is critical for the virulence of several pathogenic bacteria, including enteropathogenic Escherichia coli (EPEC). EPEC T3SS activation is associated with repression of carbon storage regulator (CsrA), resulting in gene expression remodeling, which is known to affect EPEC central carbon metabolism and contributes to the adaptation to a cell-adherent lifestyle in a poorly understood manner. We reasoned that the changes in the bacterial envelope upon attachment to the host and the activation of a secretion system may involve a modification of the lipid composition of bacterial envelope. Accordingly, we performed a lipidomics analysis on mutant strains that simulate T3SS activation. We saw a shift in glycerophospholipid metabolism toward the formation of lysophospholipids, attributed to corresponding upregulation of the phospholipase gene and the acyltransferase gene upon T3SS activation in EPEC. We also detected a shift from menaquinones and ubiquinones to undecaprenyl lipids, concomitant with abnormal synthesis of O antigen. The remodeling of lipid metabolism is mediated by CsrA and associated with increased bacterial cell size and zeta potential and a corresponding alteration in EPEC permeability to vancomycin, increasing the sensitivity of T3SS-activated strains and of adherent wild-type EPEC to the antibiotic. The characterization of EPEC membrane lipid metabolism upon attachment to the host is an important step toward a better understanding the shift of EPEC, a notable human pathogen, from a planktonic to adherent lifestyle. It may also apply to other pathogenic bacteria that use this secretion system. We predict that upon attachment to host cells, the lipid remodeling upon T3SS activation contributes to bacterial fitness and promotes host colonization, and we show that it is associated with increased cell permeability and higher sensitivity to vancomycin. To the best of our knowledge, this is the first demonstration of a bacterial lipid remodeling due to activation of a secretion system.
革兰氏阴性菌的细胞包膜是一种复杂的结构，对细菌的生存和对许多抗生素的耐药性至关重要。穿过细菌包膜和宿主细胞膜的通道形成分泌系统，这些系统在与宿主附着时被激活，使细菌能够将效应分子注入宿主细胞，这是细菌与宿主相互作用所必需的。III 型分泌系统（T3SS）对于几种致病性细菌的毒力至关重要，包括肠致病性大肠杆菌（EPEC）。EPEC T3SS 的激活与碳储存调节剂（CsrA）的抑制有关，导致基因表达重塑，这已知会影响 EPEC 的中心碳代谢，并以一种尚未完全理解的方式有助于适应细胞附着的生活方式。我们推断，在附着到宿主时，细菌包膜的变化和分泌系统的激活可能涉及细菌包膜脂质组成的修饰。因此，我们对模拟 T3SS 激活的突变菌株进行了脂质组学分析。我们看到甘油磷脂代谢向溶血磷脂的形成发生转变，这归因于 T3SS 在 EPEC 中激活时磷脂酶基因 和酰基转移酶基因 的相应上调。我们还检测到从menaquinones 和 ubiquinones 到 undecaprenyl lipids 的转变，同时 O 抗原的合成异常。脂质代谢的重塑由 CsrA 介导，并与细菌细胞大小和 ζ 电位的增加以及 EPEC 对万古霉素通透性的相应改变有关，从而增加了 T3SS 激活株和附着野生型 EPEC 对该抗生素的敏感性。对 EPEC 附着到宿主时膜脂质代谢的表征是更好地理解 EPEC 从浮游生物到附着生活方式转变的重要一步，EPEC 是一种重要的人类病原体。它也可能适用于其他使用这种分泌系统的致病性细菌。我们预测，在附着到宿主细胞后，T3SS 激活引起的脂质重塑有助于细菌的适应性，并促进宿主定植，我们还表明它与细胞通透性增加和对万古霉素的敏感性增加有关。据我们所知，这是首次证明由于分泌系统的激活而导致细菌脂质重塑。
