REPLACEMENT THERAPY OF DENTAL CARIES

修订后的竞争性续期申请提出了以下研究： 进一步发展替代疗法，作为预防 人类的龋齿 三个项目的第一个细节 变异链球菌效应菌株的构建方法 结合了低毒性和强定殖的特性 潜力 前一种性质由乳酸脱氢酶实现 使菌株产酸较少的缺陷。 后一个属性 依赖于产生高水平的小细菌素样 抑制其他链球菌生长的分子。变异株 效应菌株的构建将使用重组DNA方法， 产生完全稳定的遗传上明确定义的效应菌株 回归。 第二个项目描述了分析重组效应子的方法， 关于其在替代疗法中的服务能力， 龋病 其发酵终产物的谱和水平 将被确定，其细菌素的特异性和效力也将被确定， 像活动。 效应菌株的致龋潜力将是 在三种不同的大鼠模型中进行了分析。 它对生态的影响 将研究牙菌斑和对动物一般健康的影响。 一只老鼠 模型也将用于测试重组效应子的能力 能抢先感染链球菌变异生态位 牙齿，并积极取代土著，致病菌株， 这个微生物。 在第三个项目中，纯化的细菌素的化学组成- 将确定类似的活动。 将比较纯化的活性 在文化活动中， 活动 细菌素样活性的分子机制将是 通过确定其在靶微生物中的作用位点进行研究。 一 将使用大鼠模型来比较纯化的活性与氟化钠 作为局部抗龋齿剂。 类细菌素的作用 活性对菌斑的微生物组成和一般健康的 将对动物进行分析，作为其安全性的指标。

This revised competing renewal application proposes studies that will further develop replacement therapy as an approach for the prevention of dental caries in humans. The first of three proposed projects details methods for the construction of an effector strain of Streptococcus mutans that combines the properties of low virulence and strong colonization potential. The former property is fulfilled by lactate dehydrogenase deficiency which renders the strain less acidogenic. The latter property depends on the production of elevated levels of a small bacteriocin-like molecule that is inhibitory to the growth of other Strep. mutans strains. Construction of the effector strain will use recombinant DNA methodology to yield a genetically well-defined effector strain that is completely stable to reversion. The second project describes methods to analyze the recombinant effector strain with regard to its ability to serve in the replacement therapy of dental caries. The spectrum and levels of its fermentation end-products will be determined, as will the specificity and potency of its bacteriocin- like activity. The cariogenic potential of the effector strain will be analyzed in three different rat models. Its effects on the ecology of plaque and on the general health of the animals will be studied. A rat model will also be used to test the ability of the recombinant effector strain to preemptively colonize the Strep. mutans ecological niche on teeth, and to aggressively displace indigenous, disease-causing strains of this microorganism. In the third project, the chemical composition of the purified bacteriocin- like activity will be determined. The purified activity will be compared to the activity produced in culture with regard to its spectrum of activity. The molecular mechanism of the bacteriocin-like activity will be investigated by determining its site of action in target microorganisms. A rat model will be used to compare the purified activity to sodium fluoride as a topical anti-caries agent. The effects of the bacteriocin-like activity on the microbial composition of plaque and general health of the animals will be analyzed as measures of its safety.