Studies of genomes of dairy bacteria Lactococcus lactis

Lactococcus lactis is the bacterium, which is most common in cheese starters. It is estimated that humans annually consume more than 1018 of these bacteria. Two strains, IL1403 and MG1363, isolated from industrial sources and cured from plasmids, are used for DNA cloning and to study genetics and molecular biology of this bacterium. These strains belong to two L, lactis strain clusters called lactis and cremoris, distinct by the spectra of dairy fermentation products. To create a basis for genomic studies of L. lactis we sequenced entire genome of the strain IL1403 and performed co-linear scaffolding of the chromosome of the strain MG1363. Co-linear scaffolding consists in random sequencing of a limited number of clones and Long Range PCR mapping of the co-linear regions of the two genomes, one of which was completely sequenced earlier. In the co-linear regions, established by PCR, gene content and order should be the same. The co-linear scaffolding of the MG1363 genome, which shares 85% identity with that of IL1403, allows easy access to 50% of the genes from this strain.