Short communication: The complete genome sequence of Bifidobacterium animalis subspecies animalis ATCC 25527 ^T and comparative analysis of growth in milk with B. animalis subspecies lactis DSM 10140 ^T

The objective of this work was to sequence the genome of Bifidobacterium animalis ssp. animalis ATCC 25527 ^T, the subspecies most closely related to B. animalis ssp. lactis, some strains of which are widely added to dairy foods as probiotics. The complete 1,932,963-bp genome was determined by a combination of 454-shotgun sequencing and PCR gap closing, and the completed assembly was verified by comparison with a KpnI optical map. Comparative analysis of the B. animalis ssp. animalis ATCC 25527 ^T and B. animalis ssp. lactis DSM 10140 ^T genomes revealed high degrees of synteny and sequence homology. Comparative genomic analysis revealed 156 and 182 genes that were unique to and absent in the B. animalis ssp. animalis genome, respectively. Among these was a set of unique clustered regularly interspaced short palindromic repeats (CRISPR)-associated genes and a novel CRISPR locus containing 30 spacers in the genome of B. animalis ssp. animalis. Although previous researchers have suggested that one of the defining phenotypic differences between B. animalis ssp. animalis and B. animalis ssp. lactis is the ability of the latter to grow in milk and milk-based media, the differential gene content did not provide insights to explain these differences. Furthermore, growth and acid production in milk and milk-based media did not differ significantly between B. animalis ssp. lactis (DSM 10140 ^T and Bl04) and B. animalis ssp. animalis (ATCC 25527 ^T). Growth of these strains in supplemented milk suggested that growth was limited by a lack of available low-molecular-weight nitrogen in the 3 strains examined.