PrfA*-EXPRESSING Listeria monocytogenes CELLS ARE MORE SENSITIVE TO PEDIOCIN-LIKE PEPTIDES DESPITE IMPAIRED EXPRESSION OF THE BACTERIOCIN RECEPTOR

JUAN V. FARIZANO; MASÍAS EMILSE; CARLOS J. MINAHK; LUCILA SAAVEDRA

CABA

Congreso; REUNIÓN CONJUNTA DE SOCIEDADES DE BIOCIENCIAS; 2017

SOCIEDADES DE BIOCIENCIAS

Class IIa bacteriocins are antimicrobial peptides produced by Lactic Acid Bacteria. The accepted mechanism of action involves the permeabilization of plasma membrane, where the mannose phosphotransferase complex (Man-PTS) act as the bacteriocin receptor. As a matter of fact, the lack of expression of this complex renders cells highly resistant to these peptides. The in vitro studies on class IIa bacteriocins conducted so far dealt with bacteria in saprophytic state. Therefore, the main objective of this study was to characterize the sensitivity of L. monocytogenes cells expressing a virulent phenotype. For that purpose, we obtained cells that constitutively express an active form of the master regulator of Listeria virulence (PrfA*) by means of the pNF1002 vector. As expected, the qPCR gene expression assay of the Man-PTS subunits IIC and IID showed that those genes were downregulated in PrfA* cells. We complemented these results with a proteomic analysis of the plasma membranes. However, to our surprise, we found that these cells were more sensitive to pediocin-like peptides.Biophysical assays showed that membranes from PrfA*-expressing cells seemed to be stiffer and less compressible than the wild type cell ones. Furthermore, we performed a lipidomic analysis to determine the lipid composition of the membranes from the strains under study. This work represents the first report on the susceptibility of virulent L. monocytogenes to pediocin-like bacteriocins. In addition, it emphasizes that the current model for the interaction of bacteriocins and the receptor is incomplete and needs further development.