VALIDATION OF THE EFFECT OF INTERVENTIONS AND PROCESSES ON PERSISTENCE OF PATHOGENS ON FOODS
Location: Food Safety and Intervention Technologies
Title: Gene expression profiling of a pressure-tolerant Listeria monocytogenes Scott A CtsR deletion mutant
Submitted to: Journal of Industrial Microbiology and Biotechnology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: January 6, 2011
Publication Date: March 1, 2011
Citation: Liu, Y., Ream, A.R., Joerger, R.D., Liu, J., Wang, Y. 2011. Gene expression profiling of a pressure-tolerant Listeria monocytogenes Scott A CtsR deletion mutant. Journal of Industrial Microbiology and Biotechnology. DOI 10.1007/s10295-011-0940-9.
Interpretive Summary: The bacterium, Listeria monocytogenes, is an important food-borne pathogen that causes disease in humans and animals. High hydrostatic pressure (HPP) has been used to control L. monocytogenes in food. However, the factors that contribute to the survival of this bacterium subjected to HPP treatment remain unclear. DNA microarray technology is a powerful tool that can be used to study the expression of all of the genes possessed by a bacterium under different conditions. DNA microarrays were used to study the expression of genes in a strain of L. monocytogenes when exposed to HPP. A number of genes were found to be affected by HPP, and thus these genes could potentially be investigated as targets for strategies to increase the susceptibility of L. monocytogenes to HPP. Information from this study enhances the understanding of how L. monocytogenes survives HHP and may assist in the design of effective, economically feasible HHP food processing treatments to control this pathogen.
Listeria monocytogenes is a food-borne pathogen of significant threat to public health. High hydrostatic pressure (HPP) treatment can be used to control Listeria monocytogenes in food. The CtsR (class three stress gene repressor) protein negatively regulates the expression of class III heat shock genes. A spontaneous pressure-tolerant L. monocytogenes Scott A ctsR deletion mutant that was able to survive under HHP treatment was identified. There is currently only limited information regarding the mechanisms of survival and adaptation of L. monocytogenes to high pressure. Microarray technology was used to compare the gene expression profiles of the ctsR mutant and the wild-type strain. Total RNA was isolated from the pressure-treated (450 Mpa, 3 minutes) ctsR mutant and the wild type, labeled with fluorescent dyes, and hybridized to commercial oligonucleotide (35-mers) microarray chips representing the whole genome of L. monocytogenes. Compared to the pressure-treated L. monocytogenes Scott A wild type, 19 genes were up-regulated (> 2-fold increase) in the ctsR deletion mutant whereas 57 genes were down-regulated (< -2-fold decrease). The up-regulated genes included genes encoding for a transcriptional regulator, ATP-dependent Clp protease, putative accessory gene regulator proteins B and D, transport and binding proteins, phosphotransferase system (PTS) fructose-specific enzyme IIABC components, protein synthesis, and hypothetical proteins. The down-regulated genes included genes that encode for the PTS system, mannose-specific IIABCD components, transport and binding proteins, flagella synthesis-related proteins, a transcriptional regulator, and hypothetical proteins. The gene expression changes determined by microarray assays were confirmed by real-time RT-PCR analyses. This study enhances our understanding of how Listeria monocytogenes survives HHP and may assist in the design of effective, economically feasible HHP food processing treatments to control this pathogen.