Differential roles of the two-component peptides of lactocin 705 in antimicrobial activity

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Abstract. Lactobacillus casei CRL705 produces a class IIb bacteriocin, lactocin 705, which relies on the complementary action of two components, Lac705a and Lac705b. These peptides exert a bactericidal effect on the indicator strain Lactobacillus plantarum CRL691, with an optimal Lac705a/Lac705b peptide ratio of 1 to 4. Electron microscopy studies showed that treated CRL691 cells have their cell wall severely damaged, with mesosome-like membranous formations protruding into their cytoplasm. Although less pronounced, a similar effect was also observed with the Lac705_ peptide alone. Furthermore, Lac705b increased the inhibitory action of a diluted supernatant of L. casei CRL705, while Lac705a protected CRL691 cells from inhibition. Both peptides were required to dissipate the proton motive force(DY and DpH) of CRL691 cells. These data suggested that of the two components of lactocin 705, the Lac705a peptide is responsible for receptor recognition, and the Lac705b peptide is the active component on the cell membrane of CRL691 cells. Información suministrada por el agente en SIGEVA