Biochimie des Interactions Macromoléculaires, Institut Pasteur, CNRS UMR3528, Université Paris Cité, Paris, France.
Proteomic Platform, Mass Spectrometry for Biology Unit, Institut Pasteur, CNRS UAR 2024, Université Paris Cité, Paris, France.
PLoS One. 2023 Sep 15;18(9):e0291736. doi: 10.1371/journal.pone.0291736. eCollection 2023.
In many Gram-negative bacteria, the stress sigma factor of RNA polymerase, σS/RpoS, remodels global gene expression to reshape the physiology of stationary phase cells and ensure their survival under non-optimal growth conditions. In the foodborne pathogen Salmonella enterica serovar Typhimurium, σS is also required for biofilm formation and virulence. We have recently shown that a ΔrpoS mutation decreases the magnesium content and expression level of the housekeeping Mg2+-transporter CorA in stationary phase Salmonella. The other two Mg2+-transporters of Salmonella are encoded by the PhoP-activated mgtA and mgtB genes and are expressed under magnesium starvation. The σS control of corA prompted us to evaluate the impact of CorA in stationary phase Salmonella cells, by using global and analytical proteomic analyses and physiological assays. The ΔcorA mutation conferred a competitive disadvantage to exit from stationary phase, and slightly impaired motility, but had no effect on total and free cellular magnesium contents. In contrast to the wild-type strain, the ΔcorA mutant produced MgtA, but not MgtB, in the presence of high extracellular magnesium concentration. Under these conditions, MgtA production in the ΔcorA mutant did not require PhoP. Consistently, a ΔmgtA, but not a ΔphoP, mutation slightly reduced the magnesium content of the ΔcorA mutant. Synthetic phenotypes were observed when the ΔphoP and ΔcorA mutations were combined, including a strong reduction in growth and motility, independently of the extracellular magnesium concentration. The abundance of several proteins involved in flagella formation, chemotaxis and secretion was lowered by the ΔcorA and ΔphoP mutations in combination, but not alone. These findings unravel the importance of PhoP-dependent functions in the absence of CorA when magnesium is sufficient. Altogether, our data pinpoint a regulatory network, where the absence of CorA is sensed by the cell and compensated by MgtA and PhoP- dependent mechanisms.
在许多革兰氏阴性菌中，RNA 聚合酶的应激σ因子σS/RpoS 重塑了全局基因表达，重塑了静止期细胞的生理学特性，并确保了它们在非最佳生长条件下的存活。在食源性病原体鼠伤寒沙门氏菌中，σS 也需要生物膜形成和毒力。我们最近表明，ΔrpoS 突变会降低静止期鼠伤寒沙门氏菌中管家 Mg2+转运蛋白 CorA 的镁含量和表达水平。沙门氏菌的另外两种 Mg2+转运蛋白由 PhoP 激活的 mgtA 和 mgtB 基因编码，并在镁饥饿时表达。σS 对 corA 的控制促使我们通过全基因组和分析蛋白质组学分析和生理测定来评估 CorA 在静止期沙门氏菌细胞中的影响。ΔcorA 突变赋予了从静止期退出的竞争劣势，并且略微损害了运动性，但对总细胞和游离细胞镁含量没有影响。与野生型菌株相比，在高细胞外镁浓度存在的情况下，ΔcorA 突变体产生 MgtA，但不产生 MgtB。在这些条件下，ΔcorA 突变体中 MgtA 的产生不需要 PhoP。一致地，ΔmgtA，但不是 ΔphoP，突变略微降低了 ΔcorA 突变体的镁含量。当 ΔphoP 和 ΔcorA 突变组合时观察到合成表型，包括在独立于细胞外镁浓度的情况下，生长和运动性的强烈降低。ΔcorA 和 ΔphoP 突变组合而非单独突变降低了几个与鞭毛形成、趋化性和分泌有关的蛋白质的丰度。这些发现揭示了在镁充足时，CorA 缺失时 PhoP 依赖性功能的重要性。总之，我们的数据确定了一个调控网络，其中细胞感知到 CorA 的缺失，并通过 MgtA 和 PhoP 依赖性机制进行补偿。
