In the food industry, lots of control technologies are conducted to prevent microbial contamination during food processing and storage. Among these methods, H2O2 is well known as an antibacterial reagent in food safety process. However, the sub-lethal concentrations for preserving the food quality and flavor during food processing can enable foodborne bacteria to adapt to the antibacterial effect.
In response to sub-lethal H2O2 stress, 965 genes of Salmonella enterica serovar Typhimurium 14028S genome were significantly changed in their expression according to transcriptomic analysis. These differentially expressed genes (DEGs) were subjected to qRT-PCR to validate their expression profiles and 14 genes were further selected to define their roles in Salmonella resistance under H2O2 stress. Nine mutant strains lacking 4 genes and 5 operons were constructed individually and among these mutant strains, ΔkatN mutant strain was significantly attenuated in its survival after H2O2 treatments. Given that gene katN is known to encode KatN catalase which resolves H2O2 to H2O and O2 using Mn as a cofactor, genes of mntH and sitABCD encoding distinct Mn transporters were deleted and bacterial resistance against H2O2 treatments was examine. Mutant strains lacking both of Mn transporters and lacking the Mn transporters and the KatN catalase showed significant decreases in those viabilities after H2O2 treatments. Salmonella supplemented with Mn was less susceptible to H2O2 treatments when compared with the case without Mn. The beneficial effect of Mn addition was still observed in the ΔmntH or ΔsitABCD mutant strains. However, Mn addition failed to supplement bacterial H2O2 resistance in the absence of both transporters. In addition, Mn-associated H2O2 detoxification was abolished when EDTA was added as a Mn chelator. Considering the roles of coordinated action among KatN, MntH, and SitABCD in H2O2 resistance, these factors can be promising control targets for preventing Salmonella contamination and resistance in food industry.
