牙菌斑生物膜胞外多糖中间体结构的转换模式及其调控机制研究

The extracellular polysaccharide, wich provides a scaffold for the biofilms,contributes to the cariogenicity of the dental plaque. The structural transformation between the water-soluble glucans and water-insoluble glucans plays a crucial role in the biofilms organization, bacterial metabolism, and the cariogenicity. The previous study made by the applicant team via the glycomics techniques showed that there was an intermediate structure existing during the the structural transformation between the water-soluble glucans and water-insoluble glucans, which may related to the pathogenicity of the cariogenic dental plaque biofilm. The applicant hereby put forward a new hypothesis that the intermediate structure modulates structural transformation between the water-soluble glucans and water-insoluble glucans which may play an important role in the cariogenicity of the dental plaque. In order to verify the hypothesis, the applicants will adopt synthetically the methods of microbiological and molecular biological techniques, laser scanning confocal microscopy, and fluorigenic labeling technique to investigate the NMR spectroscopy, and GC-MS spectroscopy to investigate: (1) The biological characteristics of the intermediate structure and its relationship with cariogenicity of the biofilm; (2) The structual transformation mode between the water-soluble glucans and water-insoluble glucans modulated by the intermediate structure; (3)The role of the VicRK signal transduction system and dexA gene in the regulation of the structual transformation among water-soluble glucans, water-insoluble glucans, and the intermediate structure. This project will provide a new perspective of the exopolysaccharides structual transformation for the mechanism of the cariogenicity of the dental biofilms to pursue the new valid management for caries prevention and threpy.

胞外多糖是牙菌斑生物膜致龋的重要物质基础，而胞外多糖两个基本结构水溶性多糖(水溶体)和水不溶性多糖(水不溶体)的比例变化和相互转换在生物膜的构建、代谢及致龋作用中扮演重要角色。本课题组前期采用糖组学技术首次发现：在上述两个基本结构相互转化过程中还存在一个“中间体”结构，该结构的转换模式及方向与生物膜致龋性强弱可能相关。据此申请者提出“中间体”可介导胞外多糖水溶体-水不溶体的转换且对牙菌斑生物膜的致龋性产生重要影响的新假说。本课题拟联合采用微生物学、分子生物学、核磁共振、气相色谱-质谱分析等技术研究：①“中间体”的生物学特性及其对生物膜致龋性的影响；②“中间体”介导水溶体-水不溶体的转换模式及多糖性质的变化规律；③多糖合成通路VicRK信号通路和多糖分解基因dex等对三者转换过程的调控作用。课题以胞外多糖结构转换新模式为研究主题，为进一步阐明牙菌斑生物膜致龋机制，寻求龋病防治新途径奠定基础。

胞外多糖是牙菌斑生物膜致龋的重要物质基础，课题组立足前期研究基础及国内外进展，首次发现：在水溶性多糖(水溶体)和水不溶性多糖(水不溶体)两个基本结构相互转化过程中还存在一个“中间体”结构，该结构的转换模式及方向与生物膜致龋性强弱可能相关。据此申请人提出“中间体”可介导胞外多糖水溶体-水不溶体的转换且对牙菌斑生物膜的致龋性产生重要影响的新假说。本课题联合采用微生物学、分子生物学、渗透凝胶色谱、气相色谱-质谱分析等技术，研究发现：①而胞外多糖两个基本结构水溶性多糖(水溶体)和水不溶性多糖(水不溶体)的比例变化和相互转换在生物膜的构建及致龋作用中扮演重要角色；②胞外多糖“中间体”结构在水溶体-水不溶体的转换过程中体现为多糖分子量大小、单糖组分以及结构差异的生物学特性；③多糖合成通路vicRKX信号通路、多糖分解基因dexA以及核酸内切酶基因rnc等在水溶性多糖(水溶体)-“中间体”结构-水不溶性多糖(水不溶体)转换过程中发挥调控作用，并且三者的转换模式与生物膜致龋性密切相关。本课题以胞外多糖结构转换模式为研究主题，为进一步阐明牙菌斑生物膜致龋机制，寻求龋病防治新途径奠定基础。