LuxS系统调控变异链球菌密度感应行为，同时影响生物膜形成能力，然而LuxS密度感应与生物膜形成之间的具体机制仍不明确。Small RNAs在细菌转录后水平微调靶标基因表达，是多种细菌密度感应系统的体内效应子，目前未见报道于变异链球菌LuxS密度感应系统。申请者前期研究发现变异链球存在一类特殊的LuxS相关small RNAs（SmqsR2/4）并且可能参与调控生物膜形成。据此申请者提出变异链球菌LuxS密度感应系统通过SmqsR2/4转录后水平调控生物膜形成的科学假说。课题拟采用突变株实验、RNA近端连接检测、动物龋病模型等微生物学和分子生物学技术：1.阐明SmqsR2/4的分子生物学特性和功能；2.探究SmqsR2/4转录后水平调控生物膜形成的分子机制；3.明确SmqsR2/4对生物膜致龋性的作用效应。课题从small RNAs的核酸调控机制研究出发，以期为龋病的防治展开新的研究方向。

LuxS system mediates quorum sensing in Streptococcus mutans, also regulates biofilm formation. However, the molecular mechanism of LuxS-mediated quorum sensing to biofilm formation has been poorly understood. Small RNAs fine-tune the expression of target genes at post-transcriptional level and function as effectors of quorum-sensing signal transduction pathways in many bacteria, but the information of small RNAs in quorum sensing of S. mutans is limited. Based on the previous research, the applicant approved for the first time: the existence of specific S. mutans LuxS-related small RNAs (SmqsR2/4) and this kind of small molecules could affect biofilm formation. Therefore, the applicant hereby put forward the new hypothesis: LuxS system could regulate biofilm formation by the globally post-transcriptional repression or activation of SmqsR2/4 in S. mutans. In order to verify the hypothesis, mutant assay, in vivo RNA proximity ligation method, animal study would be applied in this project. The goal of this study was to define: the molecular and biological characteristics of SmqsR2/4; the specific molecular mechanism of SmqsR2/4 regulating biofilm formation at post-transcriptional level; the effect of SmqsR2/4 on S. mutans biofilm cariogenic pathogenicity expression. This project would focus on the SmqsRs-based bacterial riboregulation, and provide a new perspective of valid management for dental caries prevention and therapy.