Action of the two components bacteriocin lactocin 705 against Lactobacillus plantarum CRL691

CUOZZO SERGIO; CASTELLANO, P; SESMA. F; VIGNOLO, G; RAYA, R

Santa Fe, Argentina

Congreso; ENPROMER. 3rd. MERCOSUR Congress on process Systems Engeneering. 1st. Mercosur Congress on Chemical Engineering; 2001

FIQ. UNL. CERIDE. INTEC. INGAR

Abstract             Lactocin 705 is a two-component bacteriocin produced by Lactobacillus casei CRL705, a strain isolated from dry fermented sausage. In this work, the mode of action of the two peptides, of 33 amino acid residues each and termed a and b, has been evaluated against the indicator strain Lactobacillus plantarum CRL691. Lactocin 705 has a bactericide effect on sensitive CRL691 cells with a MIC of 45 nM. A different response was observed when the two peptides were added separately to a diluted supernatant of L. casei CRL705, which showed an intermediate level of inhibition on the growth of L. plantarum CRL691. While the b peptide potentiated the antimicrobial effect of the diluted supernatant, the a peptide protected CRL691 cells from inhibition when compared to the diluted supernatant alone. Electron microscopy of sensitive cells treated with lactocin 705 (a plus b) showed that the cell wall of CRL691 was severely damaged with mesosome-like membranous formations protruding into the cytoplasm. A similar effect, although less pronounced, was also observed when the b, but not the a peptide, was added alone to the cell suspension. These data suggested the b peptide as the active component of lactocin 705. Finally, a plus b peptides were as effective in dissipating the transmembrane electrical potential (DY) as valinomycin. Even though b peptide was able to produce membrane alterations, it was not capable to dissipate DY suggesting that the presence of both peptides is necessary to inhibit CRL691 cells.