A novel subtilin-like lantibiotics subtilin JS-4 produced by Bacillus subtilis JS-4, and its antibacterial mechanism against Listeria monocytogenes

The foodborne pathogen Listeria monocytogenes is the major cause of listeriosis. We isolated a novel lantibiotic subtilin JS-4 from Bacillus subtilis JS-4 and analyzed its effects against L. monocytogenes. The bacteriocin was extracted with n-butanol, purified by Sephadex LH-20 gel-filtration chromatography and semi-preparative RP-HPLC, and characterized by MALDI-TOF-MS and MALDI-TOF-MS/MS. The molecular mass of subtilin JS-4 was 3346.6 Da, and its amino acid sequence was similar to that of subtilin except for the Ala 15→Val and Leu 24→Ile substitutions. Subtilin JS-4 showed good thermal and pH stability but was inactivated by proteases. It also showed a broad antimicrobial spectrum against Gram-positive bacteria. The antibacterial mechanism of subtilin JS-4 against L. monocytogenes was investigated using confocal laser-scanning microscopy, scanning and transmission electron microscopy, which revealed that subtilin JS-4 increased cell membrane permeability, triggered K+ leakage and pore formation, damaged cell membrane integrity, altered cell morphology and intracellular organization. Taken together, subtilin JS-4 is highly effective against foodborne pathogens, and should be considered as an antibacterial preservative in the food industry.