Comparative Analysis of Listeria monocytogenes Plasmids and Expression Levels of Plasmid-Encoded Genes during Growth under Salt and Acid Stress Conditions

• Published in: Toxins Vol. 11; no. 7; p. 426
• Main Authors: Hingston, Patricia, Brenner, Thomas, Truelstrup Hansen, Lisbeth, Wang, Siyun
• Format: Journal Article
• Language: English
• Published: Switzerland MDPI AG 20.07.2019; MDPI
• Subjects: acid tolerance; Adenosine triphosphatase; Antibiotics; Cadmium; Comparative analysis; Disinfection & disinfectants; Food; food safety; Gene expression; Genes; Genomes; Heavy metals; Listeria; Listeria monocytogenes; Multicopper oxidase; NADH; NADH peroxidase; Nicotinamide adenine dinucleotide; Pathogens; Peroxidase; Phylogeny; plasmid characterization; plasmid gene expression; Plasmids; Proteins; salt tolerance; Salts; Sanitizers; Serotypes; Sodium chloride; Stresses; food safety; Listeria monocytogenes; salt tolerance; acid tolerance; plasmid gene expression; plasmid characterization
• ISSN: 2072-6651; 2072-6651
• DOI: 10.3390/toxins11070426

strains are known to harbour plasmids that confer resistance to sanitizers, heavy metals, and antibiotics; however, very little research has been conducted into how plasmids may influence ' ability to tolerate food-related stresses. To investigate this, a library ( = 93) of plasmid sequences were compared. Plasmid sequences were divided into two groups (G1 and G2) based on a phylogeny. Twenty-six unique plasmid types were observed, with 13 belonging to each of the two -based groups. G1 plasmids were significantly ( < 0.05) smaller than G2 plasmids but contained a larger diversity of genes. The most prevalent G1 plasmid (57,083 bp) was observed in 26 strains from both Switzerland and Canada and a variety of serotypes. Quantitative PCR (qPCR) revealed a >2-fold induction of plasmid-contained genes encoding an NADH peroxidase, cadmium ATPase, multicopper oxidase, and a ClpL chaperone protein during growth under salt (6% NaCl) and acid conditions (pH 5) and ProW, an osmolyte transporter, under salt stress conditions. No differences in salt and acid tolerance were observed between plasmid-cured and wildtype strains. This work highlights the abundance of specific plasmid types among food-related strains, the unique characteristics of G1 and G2 plasmids, and the possible contributions of plasmids to tolerance to food-related stresses.