Genome sequences of two strains of Lactococcus lactis subsp. cremoris with the same ancestry but a different capacity to produce exopolysaccharides

Strains of Lactococcus lactis subsp. cremoris are used to produce yogurt containing exopolysaccharides with a sticky texture. When grown at elevated temperatures, a spontaneous mutant EPSC, which had lost exopolysaccharides biosynthesis, was isolated. Genomes of the two strains were determined to be composed of a 2.4Mb chromosome and up to eleven plasmids, and it was revealed that one of the plasmids encoding the gene cluster for exopolysaccharides biosynthesis was lost selectively in EPSC.

Automated summary

Strains of Lactococcus lactis subsp. cremoris are commonly used for yogurt production with exopolysaccharides, but a mutant EPSC lacking this biosynthesis ability was isolated under elevated temperature conditions. Genomic analysis revealed the selective loss of a plasmid encoding exopolysaccharide biosynthesis cluster in EPSC, offering insights into the mechanism of exopolysaccharide synthesis in yogurt production.