Mode of action of lactocin 705, a two-component bacteriocin from Lactobacillus casei CRL705

Abstract

Lactocin 705 is a bacteriocin whose activity depends on the complementary action of two peptides (705α and 705β) 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 (ΔΨ) and the pH gradient (ΔpH). 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 Ca2+ 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.