Structural Characterization and Mode of Action Studies on Salvicin K and Antimicrobial Peptide-like Bacteriocin b Peptide Isolated from Lactobacillus salivarius K4

Abstract

Salvicin K (Sal K) and antimicrobial peptide-like bacteriocin b (Alb b) peptides produced by Lactobacillus salivarius K4 have been reported as bacteriocins from lactic acid bacteria (LAB). Here, we aimed to characterize their activity against gram-positive bacteria, Streptococcus sp. TISTR 1030 and Staphylococcus aureus TISTR 118. The antimicrobial activity increased when Sal K and Alb b peptides were combined (MIC 3.59 mM). Results from scanning electron microscope (SEM) and transmission electron microscope (TEM) showed that the bacterial cell surface altered dramatically in the presence of the Sal K and Alb b mixture. The peptide mixture affected the bacterial membrane potential and caused cell cytotoxicity leading to the leakage of DNA and b-galactosidase. Secondary structure characterization of the peptide mixtures revealed increasing helical structure in the membrane mimicking environment. From our experiments, it can be concluded that a synergistic effect is obtained when both peptides are combined presumably through the formation of a complex. Combination of peptide exhibits more active against gram-positive bacteria than each individual peptide component.