口腔细菌表面糖苷酶的生物学功能研究

Functional Studies of Glycoside Hydrolases on Oral Bacterial Cell Surface

口腔细菌是引起龋齿的关键因素。口腔细菌和黏附在牙齿表面的唾液大分子相互作用,在牙齿表面形成早期牙菌斑生物膜,随后更多的细菌加入到生物膜中生长并最终导致龋齿和牙周炎等疾病。唾液为细菌的黏附提供配体,为细菌的生长提供碳源和氮源,但是细菌如何利用以及利用哪些唾液大分子进行生长还不清楚。许多口腔细菌细胞表面和细胞内有不同的糖苷酶水解糖链。本综述总结了笔者对口腔细菌的研究,揭示不同细菌利用人的唾液生长的能力不同,有的生长良好,有的甚至不能单独在唾液中生长;而口腔共生菌Streptococcus gordonii DL1在唾液中生长良好是依赖于细菌表面的3个糖苷酶,它们捕食唾液中富含脯氨酸的糖蛋白的N-糖链,是该细菌在唾液中生长关键的第一步;而且不同的糖苷酶对底物有严格的特异性,糖链只能被依次水解。不同细菌表面有不同的糖苷酶,能够合作水解糖链从而在唾液中相互喂养并在牙齿表面共生,是笔者下一步的研究方向。

Oral bacteria play a critical role in causing dental caries.The development of earlier dental plaque has long been thought to depend on bacterial growth and sticking to teeth surface,which further recruit more bacteria growing in biofilm,and finally result in dental caries and periodontal disease.Saliva provide carbon and nitrogen source for bacterial growth.But little is known about how different oral bacteria utilize specific salivary components.Many bacteria have glycoside hydrolases on cell surface and inside cells,which can hydrolyze glycan.In this review,the recent studies on oral bacteria are summarized.We find that the growth of different oral bacteria in treated saliva is different.Some bacteria grow very well and some grow poorly or no growth.The oral commensal Streptococcus gordonii DL1 grow well in saliva,and the growth may depend on a number of glycoside hydrolases（GHs）including three cell wallanchored GHs（i.e.BgaA,StrH,EndoD）.The growth of S.gordonii DL1 in saliva depends to a significant extent on the sequential actions of BgaA followed by StrH and EndoD on N-linked glycans of PRG,which appears to be an essential first step in salivary glycans foraging.The glycoside hydrolases on the surface of different bacteria may contribute to the cross-feeding and commensal growth between bacteria on tooth surface,which will be our next research direction.