CspA regulates stress resistance, flagellar motility and biofilm formation in Salmonella Enteritidis

Abstract

Salmonella Enteritidis presents a significant challenge to food safety due to its resilience against various food-related stresses. The cold shock protein A (CspA) has been extensively studied for its role in facilitating the survival of S. Enteritidis at low temperatures. However, the broader biological functions of CspA in this pathogen remain inadequately characterized. This study aims to address this knowledge gap through a comprehensive approach involving mutagenesis, transcriptomic analysis, and phenotypic evaluation. RNA sequencing analysis identified 119 genes that were upregulated and 26 genes that were downregulated in the ΔcspA deletion mutant compared to the wild-type strain. This observation was further substantiated through the RT-qPCR technique. Functional annotation of the differentially expressed genes indicated their involvement in various pathways, such as stress resistance (4 genes), flagellar assembly (6 genes), cellular metabolism (22 genes), ATP-binding-cassette (ABC) transporters (9 genes), regulators (7 genes), and the Type III secretion system (10 genes), thus highlighting the extensive influence of CspA on bacterial gene expression. Notably, the upregulation of genes associated with acid stress response (SEN_RS08115, 10.74-fold; yhcN, 3.11-fold) and osmotic stress response (osmX, 1.69-fold; osmY, 1.50-fold) significantly enhanced the resistance of S. Enteritidis to hydrochloric acid and sodium chloride, respectively. Furthermore, approximately 20% of genes related to flagellar assembly were repressed, which resulted in swimming defects and increased auto-aggregation, thereby promoting the formation of bacterial biofilms. Overall, these findings suggest that CspA plays a pivotal role in mediating stress resistance and biofilm formation in S. Enteritidis.