NaCl stress affects the permeability of Salmonella enterica subsp. enterica Derby: a study based on comparative transcriptomics

Abstract:

[Objective] This study aims to decipher the mechanism of Salmonella enterica subsp. enterica Derby (S. Derby) adapting to hypertonic stress at the transcriptional level. We mined the differentially expressed genes (DEGs) to explore the metabolic pathways associated with the response of S. Derby to the stress. [Methods] After the hyperosmotic tolerance of S. Derby was induced, we extracted the total RNA, removed the rRNA, and constructed a cDNA library. The relevant DEGs were identified by transcriptome sequencing and bioinformatics tools and verified by real-time fluorescence quantitative PCR. [Results] After hyperosmotic stimulation, 3 950 DEGs were identified by transcriptome sequencing, which included 21 significantly up-regulated genes and 38 significantly down-regulated genes. The genes involved in the efflux of Na⁺ from the cell membrane and the metabolism of amino acids were up-regulated, which can provide energy and help S. Derby survive in a hyperosmotic environment. The genes associated with the sugar transport system (PTS), glycolysis, and anti-oxidation of S. Derby were significantly down-regulated in the stress group. Under hyperosmotic stress, the bacteria cannot take up carbohydrates from the external environment and thus the synthesis of lipopolysaccharide in the outer membrane of the cell is inhibited, which reduces the invasiveness of S. Derby, thereby increasing the toxicity of S. Derby. [Conclusion] Under saturated NaCl stress, the osmotic tolerance of S. Derby is significantly improved, during which the Na⁺/H⁺ antiporter and the glutamate metabolic pathway play a key role. The findings provide a theoretical basis for the further understanding and control of S. Derby contamination in food.