Center for Adaptation Genetics and Drug Resistance, Tufts University School of Medicine, Boston, Massachusetts, USA.
J Bacteriol. 2012 Mar;194(5):1177-85. doi: 10.1128/JB.05451-11. Epub 2011 Dec 30.
Paralogous transcriptional regulators MarA, Rob, and SoxS act individually and together to control expression of more than 80 Escherichia coli genes. Deletion of marA, rob, and soxS from an E. coli clinical isolate prevents persistence beyond 2 days postinfection in a mouse model of pyelonephritis. We used microarray analysis to identify 242 genes differentially expressed between the triple deletion mutant and its parent strain at 2 days postinfection in the kidney. One of these, znuC of the zinc transport system ZnuACB, displayed decreased expression in the triple mutant compared to that in the parental strain, and deletion of znuC from the parental strain reduced persistence. The marA rob soxS triple deletion mutant was less viable in vitro under limited-Zn and Zn-depleted conditions, while disruption of znuC caused a reduction in the growth rates for the parental and triple mutant strains to equally low levels under limited-Zn or Zn-depleted conditions. Complementation of the triple mutant with soxS, but not marA or rob, restored the parental growth rate in Zn-depleted medium, while deletion of only soxS from the parental strain led to low growth in Zn-depleted medium. Both results suggested that SoxS is a major regulator responsible for growth under Zn-depleted conditions. Gel shift experiments failed to show direct binding of SoxS to the znuCB promoter, thus suggesting indirect control of znuCB expression by SoxS. While SoxS expression in the triple mutant fully restored persistence, increased expression of znuACB via a plasmid in this mutant only partially restored wild-type levels of persistence in the kidney. This work implicates SoxS control of znuCB expression as a key factor in persistence of E. coli in murine pyelonephritis.
平行转录调控因子 MarA、Rob 和 SoxS 单独或共同作用，控制着 80 多个大肠杆菌基因的表达。在尿路感染的小鼠模型中，从大肠杆菌临床分离株中缺失 marA、rob 和 soxS 可防止其在感染后超过 2 天持续存在。我们使用微阵列分析鉴定了 242 个在感染后 2 天肾脏中三突变体与其亲本菌株之间差异表达的基因。锌转运系统 ZnuACB 的 znuC 就是其中之一，其在三突变体中的表达低于亲本菌株，而从亲本菌株中缺失 znuC 可降低其持续存在的能力。MarA-Rob-SoxS 三突变体在有限锌和缺锌条件下的体外生存能力较差，而破坏 znuC 会导致亲本和三突变体菌株的生长速率在有限锌或缺锌条件下均降低到非常低的水平。用 SoxS 而非 marA 或 rob 互补三突变体恢复了亲本菌株在缺锌培养基中的生长速率，而仅从亲本菌株中缺失 soxS 则导致其在缺锌培养基中的生长缓慢。这两个结果都表明 SoxS 是负责在缺锌条件下生长的主要调控因子。凝胶迁移实验未能显示 SoxS 与 znuCB 启动子的直接结合，因此表明 SoxS 对 znuCB 表达的间接控制。虽然三突变体中的 SoxS 表达完全恢复了持续存在能力，但通过质粒增加 znuACB 的表达仅部分恢复了肾脏中野生型水平的持续存在能力。这项工作表明 SoxS 对 znuCB 表达的控制是大肠杆菌在尿路感染中持续存在的关键因素。
