Mechanism of action of antilisterial peptides produced by Lactobacillus sakei 2a, a bacteriocin strain isolated from brasilian meat product.

KATIA GIANNI DE CARVALHO LIMA; MONIKA FRANCISCA KRUGER; MATHEUS DE SOUZA BARBOSA; EMILIANO JESUS SALVUCCI; FERNANDO SESMA; BERNADETTE DORA GOMBOSSY DE MELO FRANCO

Florida, EUA

Conferencia; IAFP 94th Annual Meeting; 2007

Introduction: Bacteriocins produced by lactic acid bacteria (LAB) are gaining increased importance due to their activity against undesirable microorganisms, especially Listeria monocytogenes, an important psichrotrophic foodborne pathogen. In previous reports, we have shown that strain Lactobacillus sakei subsp. sakei 2a, isolated from a Brazilian pork meat product, presents antilisterial activity in vitro and in situ. We also demonstrated that L. sakei 2a produces sakacin 2a and at least other eight antilisterial peptides, all active against Enterococcus faecium, Enterococcus faecalis, Staphylococcus epidermidis, Lactococcus lactis, Enterococcus hirae, Enterococcus canis, Listeria monocytogenes and Listeria inoccua. It is known that Class II bacteriocins act by altering the permeability barrier of the cellular membrane of the target cells and one of the common mechanisms of inhibition is the dissipation of the membrane potential. Purpose: The purpose of this study was to evaluate the mechanism of action of the antilisterialpeptides produced by L. sakei 2a. Materials and methods: After purification, the peptides were tested for dissipation of membrane potential and depletion of intracellular pH of L. monocytogenes, using fluorescent probes, 3,3 dipropylthiocarbocyanine iodide [DiSC3(5)] and 2,7-bis-(2carboxyethyl)5(and 6)carboxyfluorescein (BCECF), respectively (Molecular Probes). The increase of fluorescence of treated L. monocytogenes cells was measured using a Cary Eclypse Varian spectrofluorimeter. Results: All peptides decreased the membrane potential and dissipated the DpH of L. monocytogenes in a concentration-dependent fashion: 10 nM of sakacin 2a caused the same effect as 100 nM of any of the other peptides. Significance: These results indicate that the antagonist activity of L.sakei subsp. sakei 2a can be attributed to different peptides presenting similar mechanisms of action, the same described for Class II bacteriocins.