变异链球菌（变链菌）是目前公认的主要致龋菌，其对牙面的粘附是发挥致龋作用的首要条件。研究表明细菌粘附相关毒力因子的表达受细菌体内小RNA（small RNAs, sRNAs) 的调控，但sRNAs在变链菌的研究刚刚开始，其在变链菌粘附作用中的角色尚未见报道。本课题拟在不同粘附条件下对变链菌UA159的sRNAs建库、测序及筛查差异性表达的sRNAs，并应用Northern blot及RT-qPCR技术进一步鉴定。检测差异性表达sRNAs在有龋和无龋幼儿牙菌斑变链菌临床株的表达水平，结合流行病学调查资料，分析其与龋易感性的关系。预测相应靶mRNA，生物合成sRNAs后探讨龋易感性sRNAs对靶mRNA的调控作用。从转录后水平探讨变链菌的粘附机制，为寻找龋病预测及预防的新靶标提供实验依据。

Abstract: Streptococcus mutans (S. mutans) has been considered as a primary causative agent of dental caries. Their adhesion to the surface of the teeth is the prerequisite for cariogenecity. Previous studies have shown that virulence factors associated with adhesion is regulated by small RNAs (sRNAs) in bacteria. However, the study on sRNAs of S. mutans is just begining, and whether sRNAs play a role in the adhesion process of S. mutans has not been reported. This proposed project set out to address this question by constructing sRNAs libraries under various adhesion conditions in S. mutans UA159. The sRNAs showed significantly differential expression level among the various adhesion conditions will be screened out and further confirmed by Northern blot and RT-qPCR. Moreover, the relationship between differential expression sRNAs and caries susceptibility will be analyzed combining the expression of these sRNAs in children suffered from dental caries and caries free with epidemiology survey data. Furthermore, the regulatory of sRNA on target mRNAs will be explored after the prediction of target mRNAs and the biosynthesis of sRNAs. Taken together, our study not only reveal the adhesion mechanisms of S. mutans at post-transcription level, but also facilitate discovering future targets for the prediction and prevention of dental caries.