Biosynthesis, structure and function of cell wall in Streptococcus mutans

许多种乳杆菌的细胞壁由多个肽聚糖层组成 以血清型特有的多糖装饰，其特征是存在 鼠李糖。变形链球菌是人类龋齿的主要病原体，具有 还与菌血症和感染性心内膜炎有关。基于化学结构 在血清型特异性碳水化合物中，变形链球菌分为c、e、f和k型。 在口腔中发现的大约70%-80%的菌株被归类为c型。 变形链球菌的C-特异糖是由一个带有α-的多鼠李糖骨架组成。 连接的葡萄糖侧链。尽管碳水化合物的结构已被报道为 变形链球菌的血清型，我们对这些糖共聚物结构的最新见解表明 重要的功能修饰，磷酸甘油，被忽视了，可能是因为它 在纯化步骤中的损失。这一新发现证明重新检查这种化学品是合理的。 血清型特定碳水化合物的结构。拟议研究的目标之一是 用温和、无损的方法确定变形链球菌SCC的分子结构 方法：研究方法。此外，对参与依附的多酶过程知之甚少。 鳞状细胞癌多鼠李糖骨架的葡萄糖侧链与甘油的作用 变形链球菌的磷酸盐修饰。我们的初步调查结果显示，甘油 磷酸盐修饰在变形链球菌的形态、自溶、抗药性等方面起着重要作用 抗菌药物和生物被膜的形成。我们建议识别并在功能上表征 参与葡萄糖侧链与多聚鼠李糖结合的酶，并研究 甘油磷酸化修饰作用的分子机制 形态、自溶和生物膜形成。为了实现我们的目标，我们将聘用 链球菌遗传学，体外酶学，多糖的核磁共振波谱，分析 磷脂的化学、质谱学分析和各种显微镜方法 包括基于原子力显微镜的纳米机械。细胞壁生物合成机器是一种历史上 开发新型抗菌剂的首选目标。为了验证这一途径 用磷酸甘油作为SCC修饰的潜在药物靶点，我们将确定其作用 在一个大鼠龋齿模型中进行了这一修改。成功的结果将指导未来对细胞壁的研究 其他重要革兰氏阳性菌的生物发生及其新策略的开发 治疗变形链球菌感染。

The cell wall of many species of Lactobacillales consists of multiple peptidoglycan layers decorated with serotype-specific polysaccharides that are characterized by the presence of rhamnose. Streptococcus mutans is a key etiological agent of human dental caries, and has also been implicated in bacteremia and infective endocarditis. Based on the chemical structures of serotype-specific carbohydrates, S. mutans is classified into serotypes c, e, f and k with approximately 70-80% of strains found in the oral cavity classified as serotype c. The serotype c-specific carbohydrate (SCC) of S. mutans is composed of a polyrhamnose backbone with α- linked glucose side-chains. Although carbohydrate structures have been reported for all S. mutans serotypes, our recent insights into the structure of these glycopolymers indicate that the functionally important modification, glycerol phosphate, was overlooked, possibly due to its loss during the purification steps. This new finding justifies a re-examination of the chemical structures of serotype-specific carbohydrates. One of the goals of the proposed study is to determine the molecular structure of SCC isolated from S. mutans using mild, non-destructive methods. Moreover, little is known about the multienzyme processes involved in attachment of the glucose side-chains to the polyrhamnose backbone of SCC and the function of the glycerol phosphate modification in S. mutans. Our preliminary findings revealed that the glycerol phosphate modification plays important roles in S. mutans morphology, autolysis, resistance to antimicrobials and biofilm formation. We propose to identify and functionally characterize the enzymes involved in glucose side-chain attachment to polyrhamnose, and investigate the molecular mechanisms underlying the functions of glycerol phosphate modification in morphology, autolysis and biofilm formation. To accomplish our goals, we will employ streptococcal genetics, in vitro enzymology, NMR spectroscopy of polysaccharides, analytical chemistry, mass spectrometric analysis of phospholipids, and various methods of microscopy including AFM-based nanomechanics. The cell wall biosynthetic machinery is an historically preferred target for the development of novel antimicrobials. In order to validate the pathway of SCC decoration with glycerol phosphate as a potential drug target, we will determine the role of this modification in a rat caries model. Successful outcomes will guide future studies of cell wall biogenesis in other important Gram-positive bacteria and the development of novel strategies to treat S. mutans infections.