Deciphering the molecular mechanism of peracetic acid response in Listeria monocytogenes

Peracetic acid (PAA), a strong oxidizing agent, has been widely used as a disinfectant in food processing settings as it does not produce harmful chlorinated by-products. In the present study, the transcriptional response of Listeria monocytogenes to a sub-lethal concentration of PAA (2.5 ppm) was assessed using RNA-sequencing (RNA-seq). Our analysis revealed 12 differentially expressed protein-coding genes, of which nine were upregulated (ohrR, ohrA, rpsN, lmo0637, lmo1973, fur, lmo2492, zurM, and lmo1007), and three were down-regulated (argG, lmo0604 and lmo2156) in PAA-treated samples compared to the control samples. A non-coding small RNA gene (rli32) was also found to be down-regulated. In detail, the organic peroxide toxicity protection (OhrA-OhrR) system, the metal homeostasis genes fur and zurM, the SbrE-regulated lmo0636-lmo0637 operon and a carbohydrate phosphotransferase system (PTS) operon component were induced under exposure of L. monocytogenes to PAA. Hence, this study identified key elements involved in the primary response of L. monocytogenes to oxidative stress caused by PAA, including the expression of the peroxide detoxification system and fine-tuning the levels of redox-active metals in the cell. The investigation of the molecular mechanism of PAA response in L. monocytogenes is of utmost importance for the food industry, as residual PAA can lead to stress tolerance in pathogens.