沙门氏菌延滞期生长的离散规律及相关基因rpoD和rpoS的协同调控机制

Based on our previous study, the growth of Salmonella exhibit the characteristic of random and polymorphic growth during the lag phase, and the distribution of the lag phase showed the feature of discrete distribution. Besides, relevant biochemical reaction and metabolites indicated their effects on the different types of discrete distribution of the lag phase. Therefore, this research is going to study the high and low concentration of Salmonella with deterministic and stochastic model respectively. The biochemical reaction and metabolites during the lag phase would be investigated as well, so to explain the correlation between their influences on the discrete distribution. By using microarray, gene knock-out technique, quantitative real time PCR technique, to study the regulation of rpoD, rpoS, and the relevant genes during the lag phase under the stressful environment, to describe the resistance regulation system. Combine the results obtained from the cell, metabolism, and molecular studies, to establish the regulation network, and to explain the mechanism of discrete distribution of Salmonella during the lag phase. The work could not only contribute to the theory study of environmental adaptation of cells, but also could provide new ideas and methods to control and assess the safety of foods.

前期研究表明，沙门氏菌在延滞期内的生长呈现随机多态性的特征，其延滞期分布为离散型。此外，相关生物化学反应和物质代谢对其延滞期离散分布的类型具有特定的影响。鉴于此，本项目首先对沙门氏菌高浓度细胞的决定统一性生长和低浓度细胞的随机多态性生长进行模型化研究。其次，对其生化反应和代谢物质进行研究，阐明其与离散分布之间的关联和原因。应用基因芯片技术、基因重组技术、实时定量荧光PCR技术等，对主要调控基因rpoD和rpoS，及其它相关基因进行转录组的研究，以探明其应激的调控网络。最后，从系统生物学的角度，将细胞水平、代谢物质水平和分子生物学水平的结果进行结合和整理，构建沙门氏菌延滞期生长的离散规律及相关基因rpoD和rpoS的协同调控网络，从而阐明其生长离散分布的机制。通过以上研究，不仅能为探索沙门氏菌及其它细菌的环境适应性提供理论基础，也能为食品安全的保障及食品安全的风险评估提供新的思路和方发。

沙门氏菌是一种重要的人畜共患病病原菌，是引起人食源性疾病的重要原因。基于国内外研究现状和本课题组的前期工作（菌体细胞在暴露于新环境后，其延滞期的生长表现出多态性特征），重点研究沙门氏菌延滞期的生长决定模型和随机模型；沙门氏菌在高渗透压下的不同营养条件下延滞期离散生长的不同分布特征和机制；环境周期性变化对微生物适应力的影响；通过基因重组技术和转录组测序技术研究离散分布相关基因rpoS基因的调控网络；通过基因重组技术构建rpoS和rpoE双基因缺失菌株。同时，基于沙门氏菌的生长特性，建立鸡肉和生菜中沙门氏菌的生长预测模型。课题研究成果不仅可以为鸡肉和生菜污染的沙门氏菌风险评估提供一种方法，而且为探索沙门氏菌对环境压力的应激机制和交叉适应性奠定基础，这对防控食品中沙门氏菌的危害，优化食品中沙门氏菌灭菌方法和提高灭菌效果方面具有指导作用，具有较大的理论价值和现实意义。