Vitamin B₁₂-Producing Bacteria as a Nutritive Complement for a Culture of the Rotifer Brachionus plicatilis

Abstract

Out of 31 bacterial strains isolated from culture tanks of the rotifer Brachionus plicatilis, only 8 strains which were vitamin B₁₂ producers supported the growth of germ-free rotifer when they were added into yeast suspension. Of the 6 strains which were taxonomically examined, they were identified as Pseudomonas. Their vitamin B₁₂ productivity was measured by Euglena bioassay method. The concentrations of vitamin B₁₂ in the bacterial suspension were measured daily and the higbest levels of B₁₂ were estimated to be 1.2-16.5ng/ml during 8 day culture. Most (98.1-99.3%) of the vitamin B₁₂ which was produced accumulated inside the bacterial cells.
The rotifer growths were tested in batch cultures under germ-free condition, provided with vitamin B₁₂-producing bacteria as the sole food source, and with these bacteria as a complement of Nannochloropsis oculata or baker's yeast Saccharompces cerevisiae. The rotifer showed rapid growth when vitamin B₁₂ producing bacterial cells were supplied in a range of 10⁷-10¹¹cells/ml.
The results imply that in mass production tank of the rotifer vitamin B₁₂-producing bacteria might play an important role as vitamin B₁₂ supplier.