GENETIC AND BIOCHEMICAL BASES FOR S MUTANS VIRULENCE

将使用遗传、生化和免疫学方法 探讨毒力的遗传和生化基础 在变形链球菌群中，变形链球菌为远缘链球菌，远缘链球菌为S。 Crictus和鼠链霉菌(S.rattus)的致龋性。变形链球菌DNA 已经并将继续克隆到适当的 大肠杆菌K-12宿主。克隆指定信息 被认为对变形链球菌的能力有重要贡献 殖民和展示毒力将是其特征。方法 将使用克隆的基因探针来量化mrna 研究变形链球菌基因调控的水平 定殖力和毒力属性以及对 中间碳水化合物代谢。具体的项目要 要追求的是：(I)继续分子遗传学分析 SpaA基因及其蛋白的生化特性 关于它的功能和与其他表面的相互作用 大分子，(Ii)继续分子遗传学分析 Dex基因及其内源性葡聚糖酶的特性 抑制剂以确定它们在粘附性和葡聚糖中的作用 合成，(Iii)编码ASD基因的继续修饰 用于克隆的β-天冬氨酸半醛脱氢酶 媒介生物和建立ASD的调控机制(S) 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)和 开展研究以建立糖的运输机制和 利用，以及(V)克隆糖原合成和 并进行研究以确定这些基因是如何 受监管的。这些研究将有助于理解S。 变形杆菌维持新陈代谢活动，包括耐酸能力 在斑块环境中产生，随着 营养素的可获得性以及对其他 菌斑微生物。这些研究还应提供 关于变形链球菌在接触时如何保护自己的信息 环境压力，尤其是那些干扰细胞的环境压力 细胞壁或细胞膜的合成或功能。这项研究将是 符合美国国立卫生研究院重组人指南 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.