MOST-USDA Joint Research Center for Food Safety, School of Agriculture and Biology, and State Key Lab of Microbial Metabolism, Shanghai Jiao Tong University, Shanghai, China.
Molecular Characterization of Foodborne Pathogens Research Unit, Eastern Regional Research Center, Agricultural Research Service, U.S. Department of Agriculture, Wyndmoor, Pennsylvania, USA.
mSphere. 2020 Jan 8;5(1):e00638-19. doi: 10.1128/mSphere.00638-19.
The survival ability of serovar Enteritidis in antibacterial egg white is an important factor leading to outbreaks through eggs and egg products. In this study, the role of the gene , encoding an inner membrane protein, in the survival of Enteritidis in egg white, and its transcriptional regulation by CpxR were investigated. Quantitative reverse transcription-PCR (RT-qPCR) results showed that the gene expression was upregulated 35-fold after exposure to egg white for 4 h compared to that in M9FeS medium, and the deletion of () dramatically decreased the survival rate of bacteria in egg white to less than 1% of the wild type (WT) and the complementary strain at both 37 and 20°C, indicating that was essential for bacteria to survive in egg white. Furthermore, the strain was sensitive to a 3-kDa ultrafiltration matrix of egg white because of its high pH and antimicrobial peptide components. Putative conserved binding sites for the envelope stress response regulator CpxR were found in the promoter region. , the RT-qPCR assay results showed that the upregulation of in a strain in egg white was 1/5 that of the WT. , results from DNase I footprinting and electrophoretic mobility shift assays further demonstrated that CpxR could directly bind to the promoter region, and a specific CpxR binding sequence was identified. In conclusion, it was shown for the first time that CpxR positively regulated the transcription of , which was indispensable for survival of Enteritidis in egg white. serovar Enteritidis is the predominant serotype that causes human salmonellosis mainly through contaminated chicken eggs or egg products and has been a global public health threat. The spread and frequent outbreaks of this serotype through eggs correlate significantly with its exceptional survival in eggs, despite the antibacterial properties of egg white. Research on the survival mechanisms of Enteritidis in egg white will help develop effective strategies to control the contamination of eggs by this serotype and help further elucidate the complex antibacterial mechanisms of egg white. This study revealed the importance of , a gene with unknown function, on the survival of Enteritidis in egg white, as well as its transcriptional regulation by CpxR. Our work provides the basis to reveal the mechanisms of survival of Enteritidis in egg white and the specific function of the gene.
肠炎沙门氏菌在抗菌蛋清中的生存能力是通过鸡蛋和蛋制品引起感染的重要因素。本研究探讨了编码内膜蛋白的基因在肠炎沙门氏菌在蛋清中的生存能力中的作用及其受 CpxR 的转录调控。定量逆转录-PCR（RT-qPCR）结果显示，与在 M9FeS 培养基中相比，暴露于蛋清中 4 小时后，基因表达上调了 35 倍，而（）的缺失则使细菌在蛋清中的存活率显著降低至野生型（WT）和互补菌株的不到 1%，这表明该基因对于细菌在蛋清中的生存是必需的。此外，由于蛋清的高 pH 值和抗菌肽成分，菌株对蛋清的 3 kDa 超滤基质敏感。在 启动子区域发现了与 envelope stress response regulator CpxR 结合的假定保守结合位点。通过 RT-qPCR 检测，发现菌株在蛋清中的上调水平是 WT 的 1/5。DNase I footprinting 和电泳迁移率变动分析的结果进一步表明，CpxR 可以直接结合到 启动子区域，并鉴定出一个特定的 CpxR 结合序列。总之，本研究首次表明，CpxR 正向调节 基因的转录，这对于肠炎沙门氏菌在蛋清中的生存是不可或缺的。肠炎沙门氏菌是引起人类沙门氏菌病的主要血清型，主要通过受污染的鸡蛋或蛋制品传播，一直是全球公共卫生威胁。该血清型通过鸡蛋传播和频繁爆发与它在鸡蛋中的异常生存能力显著相关，尽管蛋清具有抗菌特性。研究肠炎沙门氏菌在蛋清中的生存机制将有助于制定有效的策略来控制该血清型对鸡蛋的污染，并有助于进一步阐明蛋清复杂的抗菌机制。本研究揭示了基因在肠炎沙门氏菌在蛋清中的生存中的重要性，以及 CpxR 对其转录的调控。我们的工作为揭示肠炎沙门氏菌在蛋清中的生存机制和基因的特定功能提供了基础。
