An investigation into changes in immunogenic proteins associated with cold temperature adaptation in L. monocytogenes

Listeria monocytogenes can survive under different stress conditions and its virulence appears to increase when exposed to stress factors used to control its growth. The objective of this study was to identify immunogenic proteins (IP) of L. monocytogenes associated with adaptation to cold temperature. L. monocytogenes cultures were grown at 12 and 37°C (control). Bacterial cells were collected during late exponential growth phase. The proteins were extracted, purified, quantified by BCA method, in-gel trypsin digested and analyzed by nLC-MS/MS. Proteins were identified with at least 2 peptides per protein against the L. monocytogenes Uniprot database. The IP were predicted by an in silico analysis approach. The proteins were sublocalized (Cello v2.4, SignalP 3.9) considering for the immunogenic prediction (VirulentPred) of only the non-cytosolic proteins. The IP were clusterized by STRING v11.05, applying a minimum required interaction score equal to 0.7. As result, two main different networks were determined at 12 and 37°C. In response to low temperature, proteins associated with cell motility (FliM), chemotaxis (lmo0723) and oxidative stress (sod, trxB) were identified. Moreover the above mentioned proteins are absent at 37°C. At optimal growth condition, L. monocytogenes codified for several virulence factors associated to adherence of epithelial cells (Iap) and their invasion to colonize the host gastrointestinal tract (lmo1422 and lmo0129). These results were similar to previous literature reports. the datasets obtained can be useful for further studies on listeriosis pathogenesis and role of environmental stress in determining the virulence factors expression of different strains.