Transcriptional equencing uncovers survival mechanisms of Salmonella enterica serovar enteritidis in antibacterial egg white

Authors: HUANG, XIAOZHEN - Shanghai Jiaotong University; ZHOU, XIUJUAN - Shanghai Jiaotong University; JIA, BEN - Shanghai Jiaotong University; LI, NUO - Shanghai Jiaotong University; JIA, JINGYA - Shanghai Jiaotong University; HE, MU - Shanghai Jiaotong University; HE, YICHEN - Shanghai Jiaotong University; QIN, XIAOJIE - Shanghai Jiaotong University; CUI, YAN - Shanghai Jiaotong University; SHI, CHUNLEI - Shanghai Jiaotong University; Liu, Yanhong; SHI, XIANMING - Shanghai Jiaotong University

Submitted to: mSphere
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/15/2019
Publication Date: 2/13/2019
Citation: Huang, X., Zhou, X., Jia, B., Li, N., Jia, J., He, M., He, Y., Qin, X., Cui, Y., Shi, C., Liu, Y., Shi, X. 2019. Transcriptional equencing uncovers survival mechanisms of Salmonella enterica serovar enteritidis in antibacterial egg white. mSphere. 4(1). https://msphere.asm.org/content/msph/4/1/e00700-18.full. pdf.
DOI: https://doi.org/10.1128/mSphere.00700-18

Interpretive Summary: Salmonella is a major bacterial foodborne pathogen, and there are many different types of Salmonella bacteria referred to as serotypes or serovars. One serotype within Salmonella known as Salmonella Enteritidis causes human salmonellosis primarily through consumption of eggs or egg-products. It is important to understand why this pathogen can survive in eggs and cause illness. RNA-Seq is a powerful tool that involves sequencing of nucleic acids of bacteria, and it is used to study the expression of all the bacterial genes under different conditions. RNA-Seq technology was used to study the expression of genes in S. Enteritidis when exposed to egg white, which has antimicrobial properties, to understand the mechanism this bacterium uses to adapt and survive in egg white. Genes affected with exposure to egg white were identified. The information obtained from this work can be used to develop more effective strategies for control of S. Enteritidis in eggs.

Technical Abstract: The survival mechanism of Salmonella enterica serovar Enteritidis in antibacterial egg white is not fully understood. In our lab, an egg white resistant strain S. Enteritidis SJTUF 10978 was identified. Cell envelope damage and osmotic stress response (separation of cell wall and inner membrane as well as cytoplasmic shrinkage) of this strain surviving in egg white were identified through microscopic observation. RNA-Seq analysis of the transcriptome of Salmonella survival in egg white showed that a considerable number of genes involved in DNA damage repair, alkaline pH adaptation, osmotic stress adaptation, envelope damage repair, Salmonella pathogenicity island (SPI) 2, iron absorption and biotin synthesis, were significantly up regulated (fold change = 2) in egg white, indicating these pathways or genes might be critical for bacterial survival. RNA-Seq results were confirmed by qRT-PCR and the survival analysis of six gene deletion mutants confirmed their importance in the survival of bacteria in egg white. The importance of alkaline pH adaptation and envelope damage repair for Salmonella to survive in egg white were further confirmed by analysis of deletion mutants of nhaA, cpxR, waaH and eco. According to the RNA-Seq results, we propose that alkaline pH adaptation might be the cause of bacterial osmotic stress phenotype; and that the synergistic effect between alkaline pH and other inhibitory factors can enhance the bacteriostatic effect of egg white. Moreover, cpxR and sigE were recognized as the central regulators that coordinate bacterial metabolism to adapt to envelope damage and alkaline pH.