Nguyen Trang, Zhang Zhijun, Huang I-Hsiu, Wu Chenggang, Merritt Justin, Shi Wenyuan, Qi Fengxia
UCLA School of Dentistry, Los Angeles, CA 90095, USA.
College of Dentistry, University of Oklahoma Health Sciences Center, Oklahoma City, OK 73034, USA.
Microbiology (Reading). 2009 Feb;155(Pt 2):551-556. doi: 10.1099/mic.0.021303-0.
Streptococcus mutans is considered a primary pathogen for human dental caries. Its ability to produce a variety of peptide antibiotics called mutacins may play an important role in its invasion and establishment in the dental biofilm. S. mutans strain UA140 produces two types of mutacins, the lantibiotic mutacin I and the non-lantibiotic mutacin IV. In a previous study, we constructed a random insertional-mutation library to screen for genes involved in regulating mutacin I production, and found 25 genes/operons that have a positive effect on mutacin I production. In this study, we continued our previous work to identify genes that are negatively involved in mutacin I production. By using a high-phosphate brain heart infusion agar medium that inhibited mutacin I production of the wild-type, we isolated 77 clones that consistently produced mutacin I under repressive conditions. From the 34 clones for which we were able to obtain a sequence, 17 unique genes were identified. These genes encompass a variety of functional groups, including central metabolism, surface binding and sugar transport, and unknown functions. Some of the 17 mutations were further characterized and shown to increase mutacin gene expression during growth when the gene is usually not expressed in the wild-type. These results further demonstrate an intimate and intricate connection between mutacin production and the overall cellular homeostasis.
变形链球菌被认为是人类龋齿的主要致病菌。其产生多种称为变链菌素的肽类抗生素的能力可能在其侵入和在牙菌斑中定殖过程中发挥重要作用。变形链球菌UA140菌株产生两种类型的变链菌素,即羊毛硫抗生素变链菌素I和非羊毛硫抗生素变链菌素IV。在先前的一项研究中,我们构建了一个随机插入突变文库,以筛选参与调节变链菌素I产生的基因,并发现了25个对变链菌素I产生有正向作用的基因/操纵子。在本研究中,我们继续之前的工作,以鉴定对变链菌素I产生有负向作用的基因。通过使用抑制野生型变链菌素I产生的高磷酸盐脑心浸液琼脂培养基,我们分离出了77个在抑制条件下持续产生变链菌素I的克隆。从我们能够获得序列的34个克隆中,鉴定出了17个独特的基因。这些基因涵盖了多种功能类别,包括中心代谢、表面结合和糖转运以及未知功能。对这17个突变中的一些进行了进一步表征,结果表明,当该基因在野生型中通常不表达时,这些突变会在生长过程中增加变链菌素基因的表达。这些结果进一步证明了变链菌素产生与整体细胞内稳态之间存在密切而复杂的联系。