Effect of vitamin B12 and its lower ligand a-ribazole supply on composition of prokaryotic and protist communities in oceanic systems

The cofactor vitamin B12 is produced by only one-third of all prokaryotes but almost all encode at least one B12-dependent enzyme, implying that the majority of prokaryotes relies on exogenous B12 supply and interact with producers. We conducted mesocosm experiments in in the south-subtropical, equatorial and northern polar frontal Pacific Ocean to test whether supply by B12 and α-ribazole, the lower ligand of vitamin B12, can enhance heterotrophic prokaryotic production and can alter the composition of prokaryotic and heterotrophic protist communities