State Key Laboratory of Virology, Wuhan Institute of Virology, The Chinese Academy of Sciences, Wuhan, Hubei Province, China.
FEMS Microbiol Lett. 2011 Apr;317(2):190-5. doi: 10.1111/j.1574-6968.2011.02227.x. Epub 2011 Mar 1.
Survival in acidic environments is important for successful infection of gastrointestinal pathogens. Many bacteria have evolved elaborate mechanisms by inducing or repressing gene expression, which subsequently provide pH homeostasis and enable acid survival. In this study, we employed comparative proteomic analysis to identify the acid-responsive proteins of a food-borne enteric bacterium, Yersinia pseudotuberculosis. The expression level of eight proteins involved in carbohydrate metabolism was up- or downregulated over twofold at pH 4.5 compared with pH 7.0. The role of a global transcriptional regulator catabolite repressor/activator Cra was further studied in this acid survival process. lacZ-fusion analysis showed that expression of cra was repressed under acidic pH. Deletion of the cra gene increased acid survival by 10-fold, whereas complementation restored the wild-type phenotype. These results lead us to propose that, in response to acidic pH, the expression of cra gene is downregulated to increase acid survival. This is the first study to demonstrate the regulatory role of Cra in acid survival in an enteric bacterium.
在酸性环境中生存对于胃肠道病原体的成功感染很重要。许多细菌通过诱导或抑制基因表达进化出了精细的机制，从而提供 pH 平衡并实现耐酸生存。在这项研究中，我们采用比较蛋白质组学分析鉴定了食源性病原体耶尔森氏菌 Yersinia pseudotuberculosis 的酸响应蛋白。与 pH7.0 相比，在 pH4.5 时，涉及碳水化合物代谢的 8 种蛋白质的表达水平上调或下调了两倍以上。在这个耐酸生存过程中，我们进一步研究了全局转录调节因子分解代谢物阻遏物/激活物 Cra 的作用。lacZ 融合分析表明，在酸性 pH 下，cra 基因的表达受到抑制。cra 基因缺失使耐酸能力提高了 10 倍，而互补则恢复了野生型表型。这些结果使我们提出，为了应对酸性 pH，cra 基因的表达下调以增加耐酸能力。这是首次证明 Cra 在肠道细菌耐酸生存中的调节作用的研究。
