LuxS/AI-2群体感应系统调控益生乳杆菌生物被膜形成的分子机制

生物被膜是益生菌在环境胁迫中发挥生理功能的重要形式。类植物乳杆菌L-ZS9具有较高被膜形成能力及良好胃肠道耐受性与高黏附性，显示出作为益生菌制剂的潜力。全基因组测序发现，L-ZS9含有LuxS/AI-2群体感应（quorum sensing，QS）系统关键基因luxS，外源补充AI-2信号分子及其阻断剂D-ribose可明显影响被膜形成量，初步表明该系统参与了被膜的形成。本项目拟通过构建luxS缺失株、过表达株及外源补充AI-2来验证luxS功能，明确该系统对被膜的调控作用；利用RNAseq和iTRAQ技术对外源添加/不添加AI-2的luxS缺失株、过表达株及野生株进行高通量测序，在组学水平筛选差异基因/蛋白，提出被膜形成的假设性通路；进一步构建假设通路关键基因缺失株（库），通过被膜形成能力检测并结合qRT-PCR技术进行相关验证，最终从分子水平阐释QS系统调控乳杆菌生物被膜形成的机制。

Biofilm formation represents a protected mode of growth that allows probiotics to survive in hostile environments. Lactobacillus paraplantarum L-ZS9 is characterized by high gastrointestinal tolerance and adhesion ability, showing its great potential for application in probiotic products. Our previous studies have shown that L. paraplantarum L-ZS9 forms biofilm. Whole genome sequencing shows that L. paraplantarum L-ZS9 possesses gene luxS, a key gene involved in LuxS/AI-2 quorum sensing (QS). In addition, exogenous AI-2 and inhibitor D-ribose alter its biofilm formation, showing that LuxS/AI-2 QS may regulate biofilm formation of L. paraplantarum L-ZS9. In this project, the function of luxS and LuxS/AI-2 QS on biofilm formation of L. paraplantarum L-ZS9 will first be determined by the construction of mutant strains in combination with the use of exogenous AI-2. Genes and proteins potentially regulated by LuxS/AI-2 QS will then be identified by using RNAseq and iTRAQ. The functions of these genes will be validated through gene mutation, biofilm assay and qRT-PCR. This project aims at elucidating the molecular mechanisms by which LuxS/AI-2 QS regulates biofilm formation of Lactobacillus paraplantarum.