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

ABSTRACT: Listeria monocytogenes 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 L. monocytogenes' ability to tolerate food-related stresses. To investigate this, a library (n = 93) of L. monocytogenes plasmid sequences were compared. Plasmid sequences were divided into two groups (G1 and G2) based on a repA phylogeny. Twenty-six unique plasmid types were observed, with 13 belonging to each of the two repA-based groups. G1 plasmids were significantly (p < 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 L. monocytogenes strains, the unique characteristics of G1 and G2 plasmids, and the possible contributions of plasmids to L. monocytogenes tolerance to food-related stresses.

SUBMITTER: Hingston P

PROVIDER: S-EPMC6669625 | biostudies-literature | 2019 Jul

REPOSITORIES: biostudies-literature

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

Hingston Patricia P Brenner Thomas T Truelstrup Hansen Lisbeth L Wang Siyun S

Toxins 20190720 7

Listeria monocytogenes 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 L. monocytogenes' ability to tolerate food-related stresses. To investigate this, a library (n = 93) of L. monocytogenes plasmid sequences were compared. Plasmid sequences were divided into two groups (G1 and G2) based on a repA phylogeny. Twenty-six uni ...[more]

PMID: 31330827

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Project description:Listeria monocytogenes is well known to survive and grow under several stress conditions, including salt stress, which is important for growth in certain foods as well as for host infection. To characterize the contributions, to salt stress response, of transcriptional regulators important for stress response and virulence (i.e., σ(B) and PrfA), we analyzed three L. monocytogenes parent strains and isogenic mutants (ΔsigB, ΔprfA, and ΔsigBΔprfA), representing different serotypes and lineages, for their ability to grow, at 25°C, in BHI with 1.9 M NaCl. With regard to growth rate, only the lineage IV strain presented a significant difference between the parent strain and both of its respective mutants lacking prfA (ΔprfA and ΔsigBΔprfA). Conversely, the lineage I and II parent strains showed significantly shorter lag phase in comparison to their respective ΔsigB mutant strains. Intestinal epithelial cell invasion assay and hemolytic activity assays showed a significant role for σ(B) in the former and for PrfA in the latter. To explore the mechanism that may contribute to the extended lag phase in the ΔsigB mutant strain and survival and growth of the parent strain upon salt shock, whole genome transcription profiling was performed to compare transcript levels between the lineage I, serotype 1/2b, parent strain and its isogenic ΔsigB mutant after 30 min of lag phase growth at 25°C in the presence of 1.9M NaCl (salt shock) without aeration. Microarray data showed significantly higher transcript levels for 173 genes in the parent strain as compared to the ΔsigB strain. Overall, 102 of the 173 σ(B) up-regulated genes had been identified in previous studies, indicating that 71 genes were newly identified as being up-regulated by σ(B) in this study. We hypothesize that, among these genes newly identified as σ(B) up-regulated, four genes (lmo2174, lmo0530, lmo0527 and lmo0529) may play a major role in response to salt stress. Lmo2174 contains domains that facilitate sensing and producing a transduction signal in the form of cyclic di-GMP, which may activate the enzymes Lmo0527, Lmo0529 and Lmo0530, which encode proteins similar to those responsible for synthesis of exopolysaccharides that may protect the cell by changing the cell wall structure during salt stress. Overall, our data showed that σ(B), but not PrfA, contributes to growth under salt stress. Moreover, we show that the σ(B) regulon of a L. monocytogenes lineage I strain challenged with salt shock includes salt stress-specific as well as previously unidentified σ(B) up-regulated genes.

Dataset Information

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

Publications

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

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