Department of Oral Biology, College of Dentistry, University of Oklahoma Health Sciences Center, Oklahoma City, OK 73104-5419, USA.
J Bacteriol. 2010 Apr;192(7):1844-52. doi: 10.1128/JB.01667-09. Epub 2010 Jan 29.
The Streptococcus mutans hdrRM operon encodes a novel two-gene regulatory system induced by high cell density. Previous studies identified hdrM as the only known negative regulator of competence development in S. mutans. In the present study, we demonstrated that the HdrRM system bypasses the prototypical competence gene regulators ComC and ComDE in the transcriptional regulation of the competence-specific sigma factor comX and the late competence genes. Similarly, the HdrRM system can abrogate the requirement for ComE to produce the bacteriocin mutacin IV. To further probe the regulatory mechanism of hdrRM, we created an hdrR overexpression strain and showed that it could reproduce each of the hdrM competence and mutacin phenotypes, indicating that HdrM acts as a negative regulator of HdrR activity. Using a mutacin IV-luciferase reporter, we also demonstrated that the hdrRM system utilizes the same promoter elements recognized by ComE and thus appears to comprise a novel regulatory pathway parallel to ComCDE.
变形链球菌 hdrRM 操纵子编码了一种新型的双基因调控系统，该系统由高密度细胞诱导。先前的研究确定 hdrM 是变形链球菌感受态发育的唯一已知负调控因子。在本研究中，我们证明 HdrRM 系统在转录调控特异性 sigma 因子 comX 和晚期感受态基因时绕过了典型的感受态基因调控因子 ComC 和 ComDE。同样，HdrRM 系统可以消除 ComE 产生细菌素 mutacin IV 的要求。为了进一步探究 hdrRM 的调控机制，我们构建了 hdrR 过表达菌株，并表明它可以再现 hdrM 的每个感受态和 mutacin 表型，表明 HdrM 作为 HdrR 活性的负调控因子。使用 mutacin IV-荧光素酶报告基因，我们还证明 hdrRM 系统利用 ComE 识别的相同启动子元件，因此似乎构成了与 ComCDE 平行的新调控途径。
