Isolation and characterization of a salt- and oxygen-tolerant Bifidobacterium from Kishu-Narezushi

Bifidobacterium psychraerophilum was isolated from Kishu-Narezushi, marking the first discovery of the Bifidobacterium species originating from a spontaneously fermented traditional Japanese food. Kishu-Narezushi is a traditional Japanese spontaneously fermented food composed of fish, rice, and salt. Typically, Bifidobacterium species are isolated from milk-related fermented foods or human intestines. The isolated strain was identified as B. psychraerophilum and named the Yasuke strain. Bifidobacterium psychraerophilum is closely related to Bifidobacterium aquikeferi and Bifidobacterium crudilactis. The Yasuke strain and Bifidobacterium psychraerophilum DSM 22366 exhibited greater resistance to salt and oxygen compared to other Bifidobacterium species. Draft genome analysis of the Yasuke strain and four other B. psychraerophilum strains indicates the presence of stress-tolerance-related genes. Superoxide dismutase [Mn] and glutathione peroxidase genes are observed in this species. Genes involved in phage interactions, proline metabolism, and sugar and amino acid transport were uniquely identified in the Yasuke strain.