1. Mode of action of lactocin 705, a two-component bacteriocin from Lactobacillus casei CRL705
Patricia Castellano, Raul Raya, Graciela Vignolo Int J Food Microbiol. 2003 Aug 15;85(1-2):35-43. doi: 10.1016/s0168-1605(02)00479-8.
Lactocin 705 is a bacteriocin whose activity depends on the complementary action of two peptides (705alpha and 705beta) of 33-amino-acid residues each and is produced by Lactobacillus casei CRL705. Biologically active, synthetic lactocin 705 was used to study the mode of action on sensitive cells of Lactobacillus plantarum CRL691. The addition of 90 nmol l(-1) of lactocin 705 to cells of L. plantarum dissipated both, the membrane potential (DeltaPsi) and the pH gradient (DeltapH). Energized membrane, obtained after the addition of glucose, were more susceptible to lactocin 705 action leading to the immediate release of intracellular K(+) and inorganic phosphate. When the role of various ions on sensitive cells were analyzed, only Ca(2+) ion exhibited a protective effect against lactocin 705. These data suggest that the presence of a proton motive force (PMF) promotes the interaction of the bacteriocin with the cytoplasmic membrane of energized cells, leading to pore formation which allows for the efflux of ions, thereby ensuring efficient killing of target bacteria.
2. Identification and nucleotide sequence of genes involved in the synthesis of lactocin 705, a two-peptide bacteriocin from Lactobacillus casei CRL 705
S A Cuozzo, F Sesma, J M Palacios, A P de Ruíz Holgado, R R Raya FEMS Microbiol Lett. 2000 Apr 15;185(2):157-61. doi: 10.1111/j.1574-6968.2000.tb09055.x.
The structural gene determinants of lactocin 705, a bacteriocin produced by Lactobacillus casei CRL 705, have been amplified from a plasmid of approximately 35 kb and sequenced. Lactocin 705 is a class IIb bacteriocin, whose activity depends upon the complementation of two peptides (705alpha and 705beta) of 33 amino acid residues each. These peptides are synthesized as precursors with signal sequences of the double-glycine type, which exhibited high identities with the leader peptides of plantaricin S and J from Lactobacillus plantarum, brochocin C from Brochotrix campestris, sakacin P from Lactobacillus sake, and the competence stimulating peptides from Streptococcus gordonii and Streptococcus mitis. However, the two mature bacteriocins 705alpha and 705beta do not show significant similarity to other sequences in the databases.
3. Control of Listeria monocytogenes in ground beef by 'Lactocin 705', a bacteriocin produced by Lactobacillus casei CRL 705)
G Vignolo, S Fadda, M N de Kairuz, A A de Ruiz Holgado, G Oliver Int J Food Microbiol. 1996 Apr;29(2-3):397-402. doi: 10.1016/0168-1605(95)00038-0.
The effectiveness of Lactobacillus casei CRL 705 as well as that of Lactocin 705, the associated bacteriocin produced, in reducing population levels and growth of Listeria monocytogenes in sterile and non-sterile ground beef was studied. Predetermined numbers of L. monocytogenes and concentrations of Lactocin 705 were added to the meat slurries. Listeria in the bacteriocin-treated and control samples during incubation at 20 degrees C were enumerated as CFU on Bacto blood agar base. Results indicated that reduction in numbers of Listeria was largest with high levels of Lactocin 705 and few initial cell numbers of the pathogen present in the meat slurry. However, when the producer strain was added to the slurry, no significant inhibition was detected. Furthermore, inhibition by listeria was shown to be greater when meat slurries were heat-treated.
