Identification of lactose fermentation plasmids of streptococcal dairy starter strains by Southern hybridization

Abstract

Twenty-two strains of Streptococcus cremoris, seven strains of Streptococcus lactis and three strains of Streptococcus lactis subsp. diacetilactis, each with a different plasmid complement, were isolated from a starter culture used in a Finnish dairy plant. By using DNA-DNA hybridization, with cloned 6-P-s-galactosidase gene of the Strep, lactis plasmid pLP712 as a probe, the lactose fermentation genes were located, in each strain, in the large ( 30 MD) plasmid.