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 s uper o xide d ismutase ( sod )‐deletion mutant (∆ 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 ∆ sod compared to the wild type, while the expression of recA triggering SOS response, a global response to DNA damage, was increased in ∆ 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 ∆ sod survival under oxidative stress.