Establishment of taxonomic status of new prospective bacteriocin-synthesizing <Emphasis Type="Italic">Lactococci</Emphasis> strains of various origins

The taxonomic status of new prospective bacteriocin-synthesizing strains of mesophilic lactococci isolated from raw milk and milk products from different regions of Russia and also of strain F-119, obtained by protoplast fusion of two related strains with low bacteriocin-synthesizing activity, was established by classical methods of identification. The values of antibiotic activity displayed by the strains toward a test microorganism Bacillus coagulans were up to 4650 IU/ml, which is significantly higher than in natural lactococci strains. In spite of some differences in morphology, ability to ferment carbohydrates, requirements for nutrients, and antibiotic suspectability, the strains were identified as Lactococcus lactis subsp. lactis. The new strains differed from the classic nisin-producing strain L. lactis subsp. lactis MGU by a remarkably broad spectrum of bactericidal and fungicidal activity. Study of 16S rRNA gene sequences of new natural strains, fusants F-119 and another one obtained earlier, F-116, and their parental strains in comparison with reference strains confirmed the new strains’ taxonomic status as Lactococcus lactis subsp. lactis. The nucleotide sequences of 16S rRNA genes were deposited with GenBank under accession numbers EF100777-EF114305.