Lactic acid bacteria inhibit food spoilage bacteria by producing large amounts of lactic acid and growth-inhibiting peptides termed bacteriocins. Bacteriocins are ribosomally synthesized and are usually active against related species including pathogens, in particular Listeria and Enterococcus. We here isolated a bacteriocin produced by a strain called KM432Bz isolated from boza, a fermented drink usually consummed in Balkans, that we identified as a Leuconostoc pseudomesenteroides. Mass spectrometry and Edman degradation analyses performed on the bacteriocin we termed leucocin KM432Bz revealed that this antimicrobial peptide is similar to two class IIa bacteriocins, leucocins A and B and to leucocin A-QU15, discovered recently. The plasmid-located gene cluster involved in this leucocin biosynthesis was identified and analysed. Gene encoding preleucocin KM432Bz is identical to genes encoding preleucocins B and A-QU15. Leucocin KM432Bz purified from Ln. pseudomesenteroides inhibits the growth of related species such as Lactobacillus, Leuconostoc and Weissella as well as pathogenic strains like Listeria, Enterococcus and Streptococcus pneumoniae. The minimal inhibitory concentrations determined for the purified bacteriocin are included in the 0.08-10 μM range. It has also been shown here that the transcription factor s54-dependent phosphotransferase system permease of the mannose family is involved in the sensitivity of Listeria monocytogenes to the potent bacteriocin.
