Antibacterial sprectrum and mechanism of action of antilisterial peptides produced by Lactobacillus sakei 2a.

KATIA GIANNI DE CARVALHO LIMA; EMILIANO JESUS SALVUCCI; FERNANDO SESMA; BERNADETTE DORA GOMBOSSY DE MELO FRANCO

Noruega

Simposio; IX Symposium of Lactic Acid Bacteria; 2008

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. 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. The peptides P1, P3 and P5 showed a slightly larger activity spectrum against indicator strains thanpeptides wider probiotic and Gram negative strains were to In this study we report results on the mechanism of action of the peptides produced by L. sakei 2a, by means of measuring the dissipation of membrane potencial (DY), the depletion of intracellular pH (DpH) and efflux of ATP of L. monocytogenes. All peptides increased the efflux of ATP and decreased the DY and only sakacin 2a (P1) dissipated the DpH of L. monocytogenes in a concentrationdependent model: 10 nM of sakacin 2a caused the same effect as 100 nM of any of the other peptides. The addition of others peptides (P2 to P9) not dissipated the DpH of L. monocytogenes. These results indicate that the antagonist activity of L. sakei2a can be attributed to