Plasmid-encoded determinants for bacteriocin production and immunity in a Lactococcus lactis strain and purification of the inhibitory peptide.

ABSTRACT

Lactococcin, a bacteriocin produced by Lactococcus lactis subsp. lactis ADRIA 85LO30, was purified as a 2.3-2.4 kDa peptide. Six non-bacteriocin-producing (Bac-) and non-immune (Imm-) strains were isolated after curing experiments. These strains had in common the loss or modification of two plasmids pOS4 (32 kb) and pOS5 (70 kb). By comparing pOS5 and several modified plasmids, a DNA region from pOS5 of about 10 kb, which was necessary for wild-type bacteriocin production and immunity, was identified.