Whole proteomics analysis of a Listeria monocytogenes 1/2a strain exposed at different stress conditions

Listeria monocytogenes is considered as one of the most severe foodborne agents causing listeriosis outbreaks, a systemic illness due to ingestion of contaminated food. Listeriosis has a fatality rate of 20-30% [1]. The pathogen is widely spread in nature and can survive in hostile environments, such as high salt, low temperature, and low pH. This study aims to investigate the whole proteome of a L. monocytogenes 1/2a strain, grown at 4 different combinations of temperature, pH, and sodium chloride (C1 control: 37°C, pH 7.0, NaCl 0.5%; C2: 37°C, pH 5.5, NaCl 7%; C3: 12°C, pH 7, NaCl 0.5%; C4: 12°C, pH 5.5, NaCl 7%). The total cell lysate of each condition was resolved by SDS-PAGE for running immunoblotting and nLC-MS/MS based proteomics analysis. A total of 1 160 proteins were identified against L. monocytogenes uniprot database with 2 peptides per protein as minimum. By gene ontology enrichment analysis, it was observed that in response to the high osmolarity and acidic stress, L. monocytogenes survived enriching the pathway of the cellular component biogenesis, modulating cell membrane lipid composition and amino acid metabolism, and acting on the amino acid-dependent acid tolerance systems. Furthermore, modulation of lipids biosynthesis was adopted to overcome the issue of low temperature in C3. In response to a combination of stress parameters in C4, L. monocytogenes adapted itself regulating the enrichment of the response to environmental stimuli and modulating the abovementioned pathways, as well as DNA repair. Grouping the genes by functional categories, differently by C1, the number of genes involved in the pathogenesis pathway were higher compared with the other conditions. Overall, the data obtained by this study are interesting to better understand L. monocytogenes metabolism when exposed at different stress conditions. Further data analyses will be performed by mean of bioinformatic tools (i.e., VirulentPred and Vaxijen) to identify the potential immunogenic proteins involved in the virulence pathways of this microorganism.