单增李斯特菌DegU直接调控CtsR介导的温度适应

Listeria monocytogenes DegU directly regulates the CtsR to mediate temperature adaption

在食品加工过程中温和的热处理方式难以完全消灭耐热性强的食源性单增李斯特菌,该菌对食品安全构成显著风险。团队前期发现李斯特菌孤儿反应调节因子DegU与细菌的耐热应激密切相关,为进一步探索DegU参与温度适应调控的分子机制,本研究以单增李斯特菌EGD-e为参考菌株,利用同源重组方法构建单增李斯特菌基因缺失株ΔdegU和回补株CΔdegU,在前期基础上挖掘DegU调控单增李斯特菌适应环境温度的相关分子机制。研究结果显示:荧光定量PCR试验发现单增李斯特菌缺失degU后导致基因ctsR(编码应激调节因子CtsR)的转录水平显著降低;凝胶迁移阻滞试验首次证明DegU能与基因ctsR的启动子区结合,表明DegU以直接方式调控ctsR。综上,本研究发现DegU通过直接调控应激调节因子CtsR的表达适应环境温度变化,为进一步深入理解单增李斯特菌等重要人兽共患病原菌适应环境应激过程中的调控机制奠定了研究基础,具有重要的公共卫生学意义。

It is difficult to completely eliminate foodborne Listeria monocytogenes(L.monocytogenes)under the condition of mild heat treatment during food processing and preparation,posing a notable risk to food safety.Our previous study has determined that the orphan response regulator DegU of L.monocytogenes is closely related to the ability to resist heat stress.In order to further explore the regulatory mechanism,in this study,we constructed a degU deletion mutantΔdegU and the corresponding complementation strain CΔdegUin the background of the wild-type strain EGD-e by homologous recombination,and explored the molecular mechanism of DegU regulating the adaptation to environmental temperature based on the previous research.The result showed that the expression level of ctsR(encoding the stress response regulator CtsR)inΔdegU was significantly lower than that in EGD-e and CΔdegUstrains under the same heat stress condition,as indicated by the real-time quantitative reverse transcription PCR(qRT-PCR)assay.In addition,the electrophoretic mobility shift assay demonstrated for the first time that DegU could bind to the promoter region of ctsR,indicating that DegU directly regulates the ctsR operon.In summary,our study demonstrated that DegU mediated environmental temperature adaption by directly regulating the expression of stress response regulator CtsR.This study has great public health significance since it lays a foundation for further understanding of the regulatory mechanism of adaptation to environmental stress for zoonotic pathogens.