Impact of Sod on the Expression of Stress-Related Genes in Listeria monocytogenes 4b G with/without Paraquat Treatment

Listeria monocytogenes is a foodborne pathogen that causes listeriosis. Paraquat can generate reactive oxygen species (ROS) in cells, which results in oxidative stress. It was first shown that 1 mM of paraquat inhibited the growth rate of a superoxide dismutase (sod)-deletion mutant ({increment}sod) generated from L. monocytogenes 4b G but not in the wild-type, and induced the expression of other resistance genes (kat, fri, perR, sigB, and recA) as well as sod in the wild type. Interestingly, without paraquat treatment the expression of all the 5 genes were repressed in {increment}sod compared to the wild type, while the expression of recA triggering SOS response, a global response to DNA damage, was increased in {increment}sod in the presence of 1 mM paraquat. Taken together, these results suggest that SOD plays a central role in oxidant defense of L. monocytogenes 4b G, and SOS probably significantly impacts {increment}sod survival under oxidative stress. Practical Application: Many bacteriostatic agents and disinfectants widely used in food processing factory work by oxidation reaction. Superoxide dismutase (SOD) in pathogenic bacteria plays a role in extracellular oxidative stress resistance. This study not only showed the important role of the sod gene in anti-oxidative ability but also revealed the impact of the sod gene on the expression of other resistance genes, which contributes to understanding the action mechanism of SOD in anti-oxidation.