基于AI-2/LuxS群体感应系统的唾液乳杆菌LsZ5拮抗空肠弯曲杆菌的机制研究

AI-2/LuxS quorum sensing (QS) system mediates the intraspecies and interspecies information communication among gram-positive bacteria (G+) and gram-negative bacteria (G-). Domestic and foreign research shows that the antagonistic activities against pathogenic bacteria are associate with AI-2/LuxS QS system. Our previous study showed that Lactobacillus salivarius LsZ5 had well antagonistic activities against C.jejuni, and could express Autoinducer-2 and its supernatant could inhibit AI-2 activity of C.jejuni. However, the protective mechanism of LsZ5 is not totally understood. Based on the results in the prophase, we put forward a hypothesis that mechanism of LsZ5 against C.jejuni may be associate with the AI-2/LuxS quorum sensing. The objective of this study is to discuss the relationship of the AI-2/LuxS QS system and antibacterial effect by the method of constructing AI-2 and stain of LsZ5-luxS-, and investigate the lactobacilli functions and antagonistic mechanisms induced by AI-2/LuxS QS system via the methods of technologies of gene knockout, qPCR and genomics. At last，the effect of lactobacilli with QS system against C.jejuni was evaluated in the cell models. Our study will explore a new mechanism of probiotic lactobacilli against C.jejuni, and develop a theoretical support of probiotic properties with AI-2/LuxS QS system.

AI-2/LuxS 群体感应（QS）系统可介导革兰氏阳性和阴性菌的种内和种间交流，国内外研究表明乳杆菌AI-2/LuxS QS系统与其抑菌性相关。本课题组研究发现唾液乳杆菌LsZ5具有较好的拮抗空肠弯曲杆菌（C.jejuni）的能力，且可表达自诱导分子AI-2，抑制C.jejuni的AI-2的活性，但作用机制尚不明确。基于此，本课题以C.jejuni为研究对象，拟通过构建LsZ5的AI-2分子和LsZ5-luxS-突变株，利用基因芯片、qPCR及细胞模型等分析AI-2及luxS基因对LsZ5菌株拮抗C.ejuni的能力影响，并阐述 AI-2/LuxS QS 系统介导乳杆菌的益生特性及拮抗C.jejuni的机制，最后评价LsZ5的AI-2、突变株及野生型拮抗C.jejuni的效果。该研究将为利用乳杆菌防治C.jejuni提供新的思路，为进一步阐明乳杆菌的益生特性提供新的理论基础。

空肠弯曲杆菌（Campylobacter jejuni）是人畜共患菌，易引起食品污染及人类感染，造成巨大经济损失。研究表明乳酸菌拮抗C.jejuni的机制可能与其AI-2群体感应系统有关。基于此，本研究先通过体外筛选高产AI-2信号分子且拮抗C.jejuni的乳酸菌，发现乳酸菌体外抑制C.jejuni生长的能力与乳酸菌AI-2信号分子的表达量和细胞膜形成能力有关。在体外筛选的基础上，构建C.jejuni体内定殖小鼠模型发现乳酸菌在体内拮抗C.jejuni定殖的能力与其细胞黏附能力呈正相关。之后为模拟人体严重感染C.jejuni的病理状态及克服“定殖抗性”，利用C.jejuni和其他食源性致病菌构建多重感染模型，研究表明食源性致病菌可能通过改变小鼠肠道微生物菌群的组成及由此而带来的短链脂肪酸水平变化来影响小鼠体内C.jejuni的感染，导致宿主肠道乳酸菌属的丰度发生变化，预示乳酸菌群体效应可能影响C.jejuni的感染。在线虫模型试验中发现，乳酸菌拮抗空肠弯曲杆菌的能力与其抗氧化性具有显著相关性。此外本项目还利用筛选得到的乳酸菌开发发芽糙米乳酸菌饮料，利用天然成分抑制食源性病原菌群体效应的应用研究，为项目的成果转化奠定基础。