HEBERT Elvira Maria
congresos y reuniones científicas
Some insights of the mechanism of action of salivaricin CRL 1328 against pathogens
Rosario, Argentina
Congreso; V Congreso Argentino de MicrobiologĂ­a General SAMIGE; 2008
Salivaricin CRL1328 is a bacteriocin produced by Lactobacillus salivarius subsp. salivarius CRL1328, a human vagina isolate, that inhibits the uropathogens Neisseria ghonorroeae, Enterococcus faecalis, E. faecium, Staphylococcus saprophyticus and Streptococcus agalactiae. The final objective of our research group is the design of a probiotic product containing beneficial microorganisms, and also salivaricin, for the prevention and/or treatment of urogenital infections. In previous studies we characterized the genetic locus responsible for the bacteriocin production. Salivaricin CRL1328 is a two peptide bacteriocin whose activity depends on the complementary action of two peptides (SALa and SALb). These peptides were chemically synthesized and their biological activity was confirmed.In this work, the mechanism of the bactericidal action was studied, by using the biologically active synthetic salivaricin CRL1328 and the urogenital pathogen E. faecalis as sensitive strain. In addition, the optimal peptide ratio for bactericidal effect was analyzed. The transmembrane electrical potential was recorded by measuring the fluorescence of 3,5-dipropylthiadicarbocyanine Iodide [DiSC3(5)] using the ionophore valinomycin as control. On the other hand, the transmembrane pH gradient was determined by monitoring the fluorescence of the pH-sensitive fluorescent probe carboxy-fluorescein diacetate succinimidyl ester (cFDASE) with nigericin as control. A SALa/SALb peptide ratio of 1 to 1 was required for optimal antimicrobial effect, while the individual peptides showed no activity. Salivaricin dissipated transmembrane electrical potential of E. faecalis glucose energized cells in 50 mM K-HEPES (pH 7.0) and reduced the cFDASE fluorescence. Taken together, these data demonstrate that salivaricin CRL1328 dissipated the membrane potential and pH gradient in energized cells, leading to the collapse of the proton motive force. This action would be most likely because of the pore formation in the cytoplasmic membrane of target cells which allows the efflux of ions. Further studies are being performed to determine if this mechanism of action is similar when interacting with other uropathogens.