Project description:Peracetic acid (PAA), a strong oxidizing agent, has been widely used as a disinfectant in food processing settings as it does not produce harmful chlorinated by-products. In the present study, the transcriptional response of Listeria monocytogenes to 2.5 ppm of PAA was assessed using RNA-sequencing (RNA-seq). Our analysis revealed 12 differentially expressed genes, of which 9 were up-regulated (ohrR, ohrA, rpsN, lmo0637, lmo1973, fur, lmo2492, zurM, and lmo1007), and 3 were down-regulated (argG, lmo0604, lmo2156) in PAA treated samples compared to the control samples. A non-coding small RNA (rli32) was also found to be down-regulated. In detail, the organic peroxide toxicity protection (OhrA-OhrR) system, the metal homeostasis genes fur and zurM, the SbrE-regulated lmo0636-lmo0637 operon and a carbohydrate phosphotransferase system (PTS) operon component were induced under exposure of L. monocytogenes to PAA. Hence, this study identified key elements involved in the primary response of L. monocytogenes to oxidative stress caused by PAA. The investigation of the molecular mechanism of PAA response in L. monocytogenes is of utmost importance for the food industry, as this response can be induced in food-processing environments, as a result of inadequate rinsing during the disinfection process, that lead to PAA residues at low concentrations.
Project description:Listeria monocytogenes is a ubiquitous and psychrophilic foodborne pathogen commonly found in raw materials, ready to eat products and food environments. It was previously demonstrated that L. monocytogenes can grow faster at low temperature when unsaturated fatty acids (UFA) are present in its environment. In this study, we used comparative gene expression profiling of RNA-sequencing data to understand the impact of UFA on the behavior and cold adaptation of L. monocytogenes. We demonstrate that the incorporation of UFA into the membrane induces changes in the regulation of overall fatty acid biosynthesis, which prompts us to propose two hypotheses for UFA synthesis in L. monocytogenes. The general stress response is also highly impacted by the incorporation of UFA into the membrane at low temperature. In particular, we hypothesize that transcriptional regulation of cspB is not a temperature dependent mechanism, but could be related to a membrane fluidity stimulus. Furthermore, when UFA are incorporated into the membrane at low temperature, we observed overexpression of genes involved in flagella assembly. This study sheds light on the cold adaptation of L. monocytogenes in the presence of exogenous FA and on potential concerns for controlling these bacteria in food environments.
Project description:Persistence of Listeria monocytogenes in retail deli environments is a serious food safety issue, potentially leading to cross-contamination of ready-to-eat foods such as deli meats, salads, and cheeses. We previously discovered strong evidence of L. monocytogenes persistence in delis across multiple states. We hypothesized that this was correlated with isolates’ innate characteristics, such as biofilm-forming capacity or gene differences.We further chose four isolates for RNA-sequencing analysis and compared their global biofilm transcriptome to their global planktonic transcriptome. Analysis of biofilm vs planktonic gene expression did not show the expected differences in gene expression patterns. Overall, L. monocytogenes persistence in the deli environment is likely a matter of poor sanitation and/or facility design, rather than isolates’ biofilm-forming capacity, sanitizer tolerance, or genomic content
2021-06-11 | GSE176617 | GEO
Project description:Listeria monocytogenes sequencing under simulated food processing facility conditions.
| PRJNA554767 | ENA
Project description:Listeria monocytogenes strains isolated from two food-processing plants in Central Italy
| PRJNA689809 | ENA
Project description:Genomic characterization of Listeria monocytogenes from RTE meat products and meat processing environments in Poland
Project description:The formation of Listeria monocytogenes biofilms contributes to persistent contamination in food processing facilities. A microarray comparison of L. monocytogenes between the transcriptome of the strong biofilm forming strain (Bfms) Scott A and the weak biofilm forming (Bfmw) strain F2365 was conducted to identify genes potentially involved in biofilm formation. Among 951 genes with significant difference in expression between the two strains, a GntR-family response regulator encoding gene (LMOf2365_0414), designated lbrA, was found to be highly expressed in Scott A relative to F2365. A Scott A lbrA-deletion mutant, designated AW3, formed biofilm to a much lesser extent as compared to the parent strain by a rapid attachment assay and scanning electron microscopy. Complementation with lbrA from Scott A restored the Bfms phenotype in the AW3 derivative. A second microarray assessment using the lbrA deletion mutant AW3 and the wild type Scott A revealed a total of 304 genes with expression significantly different between the two strains, indicating the potential regulatory role of LbrA in L. monocytogenes. A cloned copy of Scott A lbrA was unable to confer enhanced biofilm forming potential in F2365, suggesting that additional factors contributed to weak biofilm formation by F2365. Findings from the study may lead to new strategies to modulate biofilm formation. Two comparisons were performed between 1) strong biofilm former Listeria monocytogenes strain ScottA versus weak biofilm former Listeria monocytogenes strain F2365; 2) Listeria monocytogenes ScottA LbrA deletion mutant strain versus Listeria monocytogenes ScottA. Four replicates were loaded for the first comparison and two replicates were loaded for the second comparison.
Project description:Beneficial bacteria with antibacterial properties are an attractive alternative to chemical-based antibacterial or bactericidal agents. The aim of our study was to source such bacteria from horticultural produce and environments and to explore the mechanisms of their antimicrobial properties. Four strains of Pseudomonas fluorescens were isolated that possessed antibacterial activity against the pathogen Listeria monocytogenes.