Vitamin B biosynthesis of isolated from the intestinal content of captive common bottlenose dolphins ().

In comparison with terrestrial mammals, dolphins require a large amount of haemoglobin in blood and myoglobin in muscle to prolong their diving time underwater and increase the depth they can dive. The genus is a common gastrointestinal bacterium in dolphins and includes two species: and . Whilst the former produces vitamin B, which is essential for the biosynthesis of haem, a component of haemoglobin and myoglobin, but not produced by mammals, the production ability of the latter remains unknown. The present study aimed to isolate from dolphins and reveal its ability to biosynthesize vitamin B. Three strains of , identified by phylogenetic analyses with 16S rRNA gene and genome-based taxonomy assignment and biochemical features, were isolated from faecal samples collected from two captive common bottlenose dolphins (). A microbioassay using ATCC 7830 showed that the average concentration of vitamin B produced by the three strains was 11 (standard deviation: 2) pg ml. The biosynthesis pathway of vitamin B, in particular, adenosylcobalamin, was detected in the draft genome of the three strains using blastKOALA. This is the first study to isolate from common bottlenose dolphins and reveal its ability of vitamin B biosynthesis, and our findings emphasize the importance of in supplying haemoglobin and myoglobin to dolphins.