Smurfit Institute of Genetics, Trinity College Dublin, Dublin 2, Ireland.
Mol Microbiol. 2010 Feb;75(4):972-89. doi: 10.1111/j.1365-2958.2009.07036.x.
In Bacillus subtilis, the WalRK (YycFG) two-component system controls peptidoglycan metabolism in exponentially growing cells while PhoPR controls the response to phosphate limitation. Here we examine the roles of WalRK and PhoPR in peptidoglycan metabolism in phosphate-limited cells. We show that B. subtilis cells remain viable in a phosphate-limited state for an extended period and resume growth rapidly upon phosphate addition, even in the absence of a PhoPR-mediated response. Peptidoglycan synthesis occurs in phosphate-limited wild-type cells at approximately 27% the rate of exponentially growing cells, and at approximately 18% the rate of exponentially growing cells in the absence of PhoPR. In phosphate-limited cells, the WalRK regulon genes yocH, cwlO(yvcE), lytE and ydjM are expressed in a manner that is dependent on the WalR recognition sequence and deleting these genes individually reduces the rate of peptidoglycan synthesis. We show that ydjM expression can be activated by PhoP approximately P in vitro and that PhoP occupies its promoter in phosphate-limited cells. However, iseA(yoeB) expression cannot be repressed by PhoP approximately P in vitro, but can be repressed by non-phosphorylated WalR in vitro. Therefore, we conclude that peptidoglycan metabolism is controlled by both WalRK and PhoPR in phosphate-limited B. subtilis cells.
在枯草芽孢杆菌中，WalRK（YycFG）双组分系统控制着指数生长期细胞的肽聚糖代谢，而 PhoPR 则控制着对磷酸盐限制的响应。在这里，我们研究了 WalRK 和 PhoPR 在磷酸盐限制细胞中肽聚糖代谢中的作用。我们表明，枯草芽孢杆菌细胞在磷酸盐限制状态下可以存活很长时间，并且在添加磷酸盐后可以迅速恢复生长，即使没有 PhoPR 介导的响应也是如此。在磷酸盐限制的野生型细胞中，肽聚糖合成的速度约为指数生长期细胞的 27%，而在没有 PhoPR 的情况下，其速度约为指数生长期细胞的 18%。在磷酸盐限制的细胞中，WalRK 调节子基因 yocH、cwlO(yvcE)、lytE 和 ydjM 的表达方式依赖于 WalR 识别序列，并且单独删除这些基因会降低肽聚糖合成的速度。我们表明，ydjM 的表达可以被 PhoP 大约 P 在体外激活，并且 PhoP 在磷酸盐限制的细胞中占据其启动子。然而，iseA(yoeB)的表达不能被 PhoP 大约 P 在体外抑制，但可以被非磷酸化的 WalR 在体外抑制。因此，我们得出结论，在磷酸盐限制的枯草芽孢杆菌细胞中，肽聚糖代谢既受 WalRK 控制，也受 PhoPR 控制。
