Submitted to: Journal of Food Science
Publication Type: Peer reviewed journal
Publication Acceptance Date: 6/19/2014
Publication Date: 9/1/2014
Citation: Suo, Y., Liu, Y., Zhou, X., Huang, Y., Shi, C., Matthews, K., Shi, X. 2014. Impact of sod on the expression of stress-related genes in Listeria monocytogenes 4b G with/without paraquat treatment. Journal of Food Science. 79(9):1745-1749. Interpretive Summary: The bacterium, Listeria monocytogenes, is an important food-borne pathogen that causes disease in humans and animals. L. monocytogenes is difficult to eliminate since it can form a biofilm (a complex aggregation of microorganisms growing on a solid substrate). To understand how biofilms are formed in L. monocytogenes, the gene that encodes for an enzyme known as superoxide dismutase was deleted from the bacterial genome forming what is referred to as a mutant strain. It was found that growth of the mutant strain was inhibited when exposed to environmental stresses that result in the formation of free radicals. In addition, five stress-related genes were induced in the mutant strain. Information from this study enhances the understanding of how L. monocytogenes tolerates stresses that the pathogen can encounter in foods and during food processing. This will help in the design of more effective control strategies.
Technical Abstract: Listeria monocytogenes is a food-borne pathogen that causes listeriosis. Paraquat can generate reactive oxygen species (ROS) in cells, which results in oxidative stress. It was firstly shown that 1 mM of paraquat inhibited the growth rate of a superoxide dismutase (sod)-deletion mutant (delta sod) generated from L. monocytogenes 4b G but not in the wild-type. However, induced expression of other resistance genes (kat, fri, perR, sigB and recA) as well as sod occurred both in delta sod mutant and in the wild-type. Interestingly, without paraquat treatment the expression of all the five genes were repressed in delta sod compared to the wild-type, while the expression of rec alpha triggering SOS response, a global response to DNA damage, was increased in delta 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 delta sod survival under oxidative stress.