鱼源产气肠杆菌QS信号分子（AHLs）的产生条件及其介导鲭鱼组胺累积的调控机制

In this project, quorum sensing (QS) signal molecule N-acyl-homoserine lactones (AHLs) produced by Enterobacter aerogenes (E. aerogenes), a high histamine-producing bacterium isolated from Chub mackerel (C. mackerel), will be investigated. Effects of nutritional and environmental factors and growth phase of bacteria on AHLs contents will be studied to determine production conditions of AHLs. By column chromatography and HPLC, AHLs will be purified and identified, and its physicochemical properties and stabilities of various conditions will also be researched. On this basis, AHLs contents, cell densities, histidine decarboxylase (HDC) activities and C. mackerel histamine contents will be measured to determine the relationship between E. aerogenes QS and histamine accumulation of C. mackerel. At the same time, the effects of different AHLs contents changed around QS starting content on expression level of HDC gene and synthesis of enzyme protein will also be explored. Subsequently, the regulation mechanism of QS signal molecule from E. aerogenes on systhesis of histamine during C. mackerel storage are revealed on the molecular biological levels. This study will further illustrate the formation way of toxic substances produced by food-borne microorganism. Meanwhile, the experimental results will also provide basic theory for developing new fresh seafood storage and safety production technology, which will prevent transmission of QS signal molecule.

本项目以源于鲭鱼的高产组胺生产菌-产气肠杆菌的群体感应（quorum sensing, QS）信号分子（N-acyl-homoserine lactones, AHLs）为研究对象，通过考察营养与环境因子和细菌生长阶段对AHLs浓度的影响，确定AHLs的产生条件；采用柱层析和高效液相色谱纯化并鉴定AHLs，探明AHLs的理化性质和影响稳定性的因素。在此基础上，测定鲭鱼贮藏过程中AHLs浓度、菌体密度、组氨酸脱羧酶（HDC）活力和鲭鱼组胺含量，确定产气肠杆菌QS与鲭鱼组胺累积的关系；同时分析QS启动阈值前后不同AHLs浓度下HDC基因的表达水平和相关酶蛋白的合成量，从分子水平上揭示产气肠杆菌QS信号分子介导鲭鱼贮藏期间组胺合成的调控机制。本研究将进一步阐明食源性微生物产生有毒物质的形成途径，其结果将为基于阻断QS信号分子传导为靶点的海洋生鲜食品贮藏保鲜和安全生产新技术的研发提供基础理论支持。

引起食品腐败的细菌中存在以N-酰基-高丝氨酸内酯（N-acyl-homoserine lactones, AHLs）为信号分子的群体感应系统，可调控食品腐败有关特性的表达。群体感应行为也是食源性微生物导致鱼类贮藏期间有毒物质产生和累积的重要途径，阻断致腐细菌之间的群体感应通讯系统，就能有效的防止食品腐败，更重要的是提高食品的安全性。本项目完成了对源于鲭鱼的高产组胺生产菌——产气肠杆菌的组氨酸脱羧酶酶学性质，信号分子AHLs的产生条件、理化性质和稳定性以及鲭鱼贮藏期间信号分子AHLs对组氨酸脱羧酶活性、组胺累积量和hdc基因表达水平的影响等方面的研究，并从酶水平和基因水平上揭示了产气肠杆菌群体感应信号分子AHLs对鲭鱼组胺产生和累积的影响以及基于AHLs调控作用的组胺合成的分子传导机制。本项目取得的研究结果可为基于阻断群体感应信号分子传导为靶点的海洋生鲜食品贮藏保鲜和安全生产新技术的研发提供基础理论支持。