METABOLIC AND STRUCTURAL CHARACTERIZATION OF ENTEROCIN CRL35-RESISTANT Listeria monocytogenes CELLS

MASIAS, EMILSE; DUPUY, FERNANDO; ACUÑA, LEONARDO; CERIONI, LUCIANA; BELLOMIO, AUGUSTO; MINAHK, CARLOS

Mar del Plata

Congreso; LI Congreso Anual de la Sociedad Argentina de Investigación Bioquímica y Biología Molecular; 2015

Enterocin CRL35 is a subclass IIa bacteriocin produced by Enterococcus mundtii CRL35 that is active against the foodborne pathogen Listeria monocytogenes. Resistant cells, that can be isolated with low frequency, constitute a great opportunity to better understand the mechanism of action of this bacteriocin. Therefore, the goal of the present work was to compare phenotypic characteristics between the sensitive strain and two resistant cells recently isolated in the lab. This study shows that mutants have a slower growth rate and lower glucose consumption, which correlated with a less pronounced acidification of the medium. Interestingly, lysozyme sensitivity was different among the cells under study. Therefore, ultrastructure was analyzed by Transmission Electron Microscopy. On the other hand, monolayer studies with purified lipid extracts indicated a more fluid and expanded state for the sensitive strains as compared to resistant ones. However, no differences in the perpendicular molecular dipole of the lipids of both sensitive and resistant cells could be measured. The stiffer films formed by lipids of the resistant strains would be due to differential fatty acid compositions. Taken together, these results indicate that both metabolic and structural modifications are involved in the resistance of Listeria cells towards enterocin CRL35.