Plasmid-associated Bacteriocin Production by and Immunity of Lactobacillus acidophilus TK8912

Lactobacillus acidophilus TK8912 produces an antibacterial substance, designated acidocin 8912, which is active against strains of Lactobacillus and Lactococcus. Of all conditions tested, the production of acidocin 8912 was maximum at 30°C in MRS broth. Acidocin 8912 was stable to heat treatment (120°C for 20min), but completely inactivated by protease treatment. Curing a plasmid pLA103 resulted in the loss of both acidocin 8912 production (Acd(+)) and host immunity (Acd(r)). A plasmid-cured strain, TK1-4 (Acd(-) Acd(8)), was transformed to Acd(+)Acd(r) with the pLA103 plasmid. These results provided the first direct evidence in lactobacilli for involvement of this plasmid in bacteriocin production and immunity.