Resolution of quorum-sensing systems in dental plaque biofilm and development of the method that prevents the plaque formation by the control of them

牙菌斑是在牙齿表面形成的生物膜，是细菌抵抗环境变化、抗生素和宿主免疫反应的保护屏障。首先，这种生物膜是由细胞外多糖（葡聚糖）形成的，这种多糖是由密炎组链球菌从糖中产生的，然后由变形组链球菌产生的粘性和不溶于水的葡聚糖加强。牙菌斑生物膜在龋的形成中起着重要的作用。在这种生物膜中，菌斑细菌通过激素等自动诱导剂与其他细菌进行交流。通过这种通常被称为群体感应的通信系统，牙菌斑中的细菌种群密度被认为是保持恒定的，并且细菌团对宿主免疫系统的构建。本研究采用基于对比CT法的实时RT-PCR分析gtfB、gtfC、gtfD、dexA和b-半乳糖苷酶基因，发现gtf和β-半乳糖苷酶基因有3个被抑制；然而，dexA上调。因此，变形链球菌可以通过平衡葡聚糖的产生和水解来控制生物膜的质量。这样的控制是必要的，以保持在光滑的表面定植，并确保外部碳水化合物存在于葡聚糖层不被使用。另一方面，进行糖基转移酶表位测定和抗糖基转移酶DNA疫苗的研制。并分析月经周期对唾液中IgA分泌及细菌数量的影响。

Dental plaque is the biofilm which is formed on the tooth surface, and is a protective barrier for the bacteria against the change of the environment, the antibiotic, and the host immune response. First this biofilm is formed by the extracellular polysaccharide(glucan), which the mitis group streptococci produce from sugar, and then is reinforced by the adhesive and water-insoluble glucan, which the mutans group streptococci produce. Dental plaque biofilm plays an important role in the caries formation. In this biofilm, the plaque bacteria communicate with other bacteria by the auto-inducer like hormone. By this communication system that is commonly known as quorum-sensing, the bacterial population density in the dental plaque is thought to be kept constant, and the bacterial mass against the host immune system is constructed.In this study, we analyzed gtfB, gtfC, gtfD, dexA, and b-galactosidase genes, using real-time RT-PCR based on the comparative CT method and demonstrated that three gtf and β-galactosidase genes were suppressed; however, dexA was upregulated. Thus, S. mutans could control biofilm mass by balancing glucan production and hydrolysis. Such control is necessary to maintain colonization on a smooth surface and to ensure that external carbohydrate present across the glucan layer is not used. On the other hand, the epitope assay of glycosyltransferase was performed and the anti-glycosyltransferase DNA vaccines were developed. Moreover, the change of the secretory IgA Secretion and the bacterial numbers in saliva by menstruation cycle were analyzed.