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，是细菌抵御环境变化、抗生素和宿主免疫反应的保护性屏障。首先，这种生物膜是由变形链球菌从糖中产生的胞外多糖(葡聚糖)形成的，然后由变形链球菌产生的粘附性和水不溶性葡聚糖加强。牙菌斑生物膜在龋病的形成中起着重要作用。在这个生物膜中，菌斑细菌通过激素等自动诱导因子与其他细菌进行交流。通过这种通常被称为群体感应的通讯系统，牙菌斑中的细菌种群密度被认为是恒定的，并构建了针对宿主免疫系统的细菌群。在本研究中，为了解决牙菌斑中的群体感应系统，我们开发了一种鉴定口腔链球菌的方法，这些细菌是这种生物膜的成员。该方法能快速鉴定口腔菌群中占60%的优势链球菌。我们发表了题为《利用16S-23S核糖体RNA基因间隔区的聚合酶链式反应快速鉴定口腔链球菌的方法》。另一方面，对2名早产儿进行了口腔菌群纵向调查，对40名1~4岁幼儿进行了口腔菌群横断面调查。结果表明，口腔菌群中α-溶血菌率随变形链球菌的抑制而降低，提示变形链球菌与α-溶血菌之间存在群体感应系统。我们已经提交了题为《变形链球菌的建立改变唾液细菌比率》的论文，我们未来的研究是鉴定变形链球菌和α-溶血菌之间产生的自我诱导子。

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 the present study, to solve the quorum-sensing system in the dental plaque, we developed the method to identify the oral streptococci, which were the members of this biofilm. This method could rapidly identify the streptococci which were dominant and occupied 60% in the oral flora. We published the paper about it entitled "Method for rapid identification of oral streptococci by PCR using 16S-23S ribosomal RNA intergenic spacer". On the other hand, we investigated the longitudinal study of oral flora against the 2 predentate infants and the cross-sectional study of oral flora against the 40 nursery school students (aged 1 to 4 years old). As a result, we demonstrated that the rate of alpha-hemolytic bacteria in oral flora decreased by the inhabitation of the mutans streptococci, suggested that the quorum-sensing system between mutans streptococci and alpha-hemolytic bacteria existed. We had submitted the paper about this entitled "Establishment of S.mutans Change Salivary Bacterial ratio".Our future study is to identify auto-inducer produced between mutans streptococci and alpha-hemolytic bacteria.