Erickson Kimberly D, Detweiler Corrella S
Department of Molecular, Cellular and Developmental Biology, University of Colorado at Boulder, Boulder, CO 80309, USA.
Mol Microbiol. 2006 Nov;62(3):883-94. doi: 10.1111/j.1365-2958.2006.05420.x. Epub 2006 Sep 29.
Bacteria utilize phosphorelay systems to respond to environmental or intracellular stimuli. Salmonella enterica encodes a four-step phosphorelay system that involves two sensor kinase proteins, RcsC and RcsD, and a response regulator, RcsB. The physiological stimulus for Rcs phosphorelay activation is unknown; however, Rcs-regulated genes can be induced in vitro by osmotic shock, low temperature and antimicrobial peptide exposure. In this report we investigate the role of the Rcs pathway using phylogenetic analysis and experimental techniques. Phylogenetic analysis determined that full-length RcsC- and RcsD-like proteins are generally restricted to Enterobacteriaceae species that have an enteric pathogenic or commensal relationship with the host. Experimental data show that RcsD and RcsB, in addition to RcsC, are important for systemic infection in mice and polymyxin B resistance in vitro. To identify Rcs-regulated genes that confer these phenotypes, we took advantage of our observation that RcsA, a transcription factor and binding partner of RcsB, is not required for polymyxin B resistance or survival in mice. S. enterica serovar Typhimurium oligonucleotide microarrays were used to identify 18 loci that are activated by RcsC, RcsD and RcsB but not RcsA. Five of the 18 loci encode genes that contribute to polymyxin B resistance. One of these genes, ydeI, was shown by quantitative real-time PCR to be regulated by the Rcs pathway independently of RcsA. Additionally, the stationary-phase sigma factor, RpoS (sigmaS), regulates ydeI transcription. In vivo infections show that ydeI mutants are out-competed by wild type 10- to 100-fold after oral inoculation, but are only modestly attenuated after intraperitoneal inoculation. These data indicate that ydeI is an Rcs-activated gene that plays an important role in persistent infection of mice, possibly by increasing bacterial resistance to antimicrobial peptides.
细菌利用磷酸化信号传递系统来响应环境或细胞内刺激。肠炎沙门氏菌编码一种四步磷酸化信号传递系统，该系统涉及两种传感激酶蛋白，即RcsC和RcsD，以及一种响应调节蛋白RcsB。Rcs磷酸化信号传递激活的生理刺激因素尚不清楚；然而，Rcs调控的基因在体外可由渗透压休克、低温和抗菌肽暴露诱导产生。在本报告中，我们使用系统发育分析和实验技术来研究Rcs途径的作用。系统发育分析确定，全长RcsC和RcsD样蛋白通常仅限于与宿主具有肠道致病或共生关系的肠杆菌科物种。实验数据表明，除RcsC外，RcsD和RcsB对小鼠的全身感染和体外对多粘菌素B的抗性也很重要。为了鉴定赋予这些表型的Rcs调控基因，我们利用了我们的观察结果，即RcsA（一种转录因子和RcsB的结合伴侣）对于多粘菌素B抗性或在小鼠中的存活不是必需的。利用肠炎沙门氏菌血清型鼠伤寒寡核苷酸微阵列来鉴定18个由RcsC、RcsD和RcsB激活但不由RcsA激活的基因座。这18个基因座中的5个编码有助于多粘菌素B抗性的基因。其中一个基因ydeI，通过定量实时PCR显示受Rcs途径调控，且不依赖于RcsA。此外，稳定期σ因子RpoS（σS）调节ydeI的转录。体内感染表明，ydeI突变体在口服接种后比野生型低10至100倍，但在腹腔接种后仅略有减弱。这些数据表明，ydeI是一个Rcs激活的基因，可能通过增加细菌对抗菌肽的抗性，在小鼠的持续感染中发挥重要作用。
