Department of Microbiology and Cell Science, Institute of Food and Agricultural Sciences, University of Florida, Gainesville, FL, United States of America.
Department of Microbial Infection and Immunity, The Ohio State University, Columbus, OH, United States of America.
PLoS One. 2019 Jan 25;14(1):e0211430. doi: 10.1371/journal.pone.0211430. eCollection 2019.
To cause infection, Salmonella must survive and replicate in host niches that present dramatically different environmental conditions. This requires a flexible metabolism and physiology, responsive to conditions of the local milieu. The sequence specific RNA binding protein CsrA serves as a global regulator that governs gene expression required for pathogenicity, metabolism, biofilm formation, and motility in response to nutritional conditions. Its activity is determined by two noncoding small RNAs (sRNA), CsrB and CsrC, which sequester and antagonize this protein. Here, we used ribosome profiling and RNA-seq analysis to comprehensively examine the effects of CsrA on mRNA occupancy with ribosomes, a measure of translation, transcript stability, and the steady state levels of transcripts under in vitro SPI-1 inducing conditions, to simulate growth in the intestinal lumen, and under in vitro SPI-2-inducing conditions, to simulate growth in the Salmonella containing vacuole (SCV) of the macrophage. Our findings uncovered new roles for CsrA in controlling the expression of structural and regulatory genes involved in stress responses, metabolism, and virulence systems required for infection. We observed substantial variation in the CsrA regulon under the two growth conditions. In addition, CsrB/C sRNA levels were greatly reduced under the simulated intracellular conditions and were responsive to nutritional factors that distinguish the intracellular and luminal environments. Altogether, our results reveal CsrA to be a flexible regulator, which is inferred to be intimately involved in maintaining the distinct gene expression patterns associated with growth in the intestine and the macrophage.
为了引起感染，沙门氏菌必须在宿主小生境中存活和复制，这些小生境呈现出截然不同的环境条件。这需要灵活的新陈代谢和生理学，以响应局部环境的条件。序列特异性 RNA 结合蛋白 CsrA 作为一种全局调节剂，调节与致病性、代谢、生物膜形成和运动相关的基因表达，以响应营养条件。其活性由两个非编码小 RNA（sRNA）CsrB 和 CsrC 决定，这两种 RNA 可隔离并拮抗该蛋白。在这里，我们使用核糖体谱和 RNA-seq 分析全面研究了 CsrA 对核糖体占据 mRNA 的影响，这是衡量翻译、转录稳定性和在体外 SPI-1 诱导条件下（模拟在肠道腔中的生长）和在体外 SPI-2 诱导条件下（模拟在巨噬细胞中的沙门氏菌包含的空泡（SCV）中的生长）的转录物稳定状态水平的一种措施。我们的发现揭示了 CsrA 在控制与应激反应、代谢和感染所需的毒力系统相关的结构和调节基因表达方面的新作用。我们观察到在两种生长条件下，CsrA 调控子存在很大差异。此外，在模拟细胞内条件下，CsrB/C sRNA 水平大大降低，并对区分细胞内和腔环境的营养因素有反应。总的来说，我们的结果表明 CsrA 是一种灵活的调节剂，它被推断与维持与在肠道和巨噬细胞中生长相关的独特基因表达模式密切相关。
