GENETIC AND BIOCHEMICAL BASES FOR S MUTANS VIRULENCE

将采用遗传学、生物化学和免疫学方法 研究致病力的遗传和生化基础 变形链球菌S. mutans、S. sobrinus，S. cricetus和S.致龋细菌的啮齿动物。 S. 变异DNA 已经并将继续被克隆到适当的 大肠杆菌K-12宿主。 克隆指定信息 被认为是重要的，有助于能力的S。变形 定殖和显示毒力的特性。 方法 将使用克隆的基因探针来定量mRNA 水平，以研究S. 变异基因 定殖和毒力属性，以及 中间碳水化合物代谢。 具体项目为 （一）继续进行分子遗传学分析， spaA基因及其蛋白的生化特性 关于其功能和与其他表面相互作用 （二）继续进行大分子的分子遗传学分析， dex基因，并表征葡聚糖酶及其内源性 抑制剂，以确定其在粘附和葡聚糖中作用 合成，（iii）继续修饰ASD基因编码 用于克隆的β-天冬氨酸半醛脱氢酶 并建立ASD监管机制 与嘧啶合成和细胞壁组装有关的基因， (iv)克隆磷酸转移酶系统（PTS）的基因， 开展研究，建立糖运输机制， 利用，和（v）用于糖原合成的克隆基因， 并进行研究，以确定这些基因是如何 监管. 这些研究将有助于理解S. 变形杆菌保持代谢活性，包括酸代谢能力。 在菌斑环境中， 营养素的有效性和对其他生物活动的反应 菌斑微生物 这些研究还应提供 关于S.变形杆菌在暴露于 环境压力，特别是那些干扰细胞的压力， 细胞壁或细胞膜的合成或功能。 这项研究将 按照NIH重组指南进行 DNA研究

Genetic, biochemical and immunological approaches will be used to investigate the genetic and biochemical bases for the virulence of the Streptococcus mutans group S. mutans, S. sobrinus, S. cricetus, and S. rattus of cariogenic bacteria. S. mutans DNA has been and will continue to be cloned into appropriate Escherichia coli K-12 hosts. Clones specifying information thought to be important in contributing to the ability of S. mutans to colonize and display virulence will be characterized. Methods will be developed using cloned gene probes to quantify mRNA levels to investigate regulation of S. mutans genes for colonization and virulence attributes and for enzymes of intermediary carbohydrate metabolism. The specific projects to be pursued are to: (i) continue molecular genetic analysis of the spaA gene and biochemical characterization of the SpaA protein in relation to its functions and interactions with other surface macromolecules, (ii) continue molecular genetic analysis of the dex gene and to characterize dextranase and its endogenous inhibitor to define their roles in adherence and in glucan synthesis, (iii) continue modification of the asd gene encoding beta-aspartate semialdehyde dehydrogenase for use in cloning vectors and to establish mechanism(s) for regulation of the asd gene in relation to pyrimidine synthesis and cell wall assembly, (iv) clone genes for the phosphotransferase system (PTS) and conduct studies to establish mechanisms for sugar transport and utilization, and (v) clone genes for glycogen synthesis and breakdown and conduct studies to determine how these genes are regulated. These studies will contribute to understanding how S. mutans maintains metabolic activity, including ability for acid production, in the plaque environment with variation in the availability of nutrients and in response to activities of other plaque microorganisms. These studies should also provide information on how S. mutans protects itself when exposed to environmental stresses, especially those that interfere with cell wall or cell membrane synthesis or function. The research will be done in conformance with the NIH guidelines for recombinant DNA research.