Production of Vitamin B₁₂ and Vitamin B₁₂ Analogues by Pure Cultures of Ruminal Bacteria

Abstract

MICROBIAL fermentation in the rumen was early recognized as the primary source of vitamin B₁₂ for the cow¹. Rumen contents contain not only the vitamin itself but also certain analogues in which the nucleotide portion of the vitamin is missing or modified by the substitution of a different benzimidazole or a purine for the base (5 : 6-dimethylbenzimidazole). In general, the analogues containing nucleotides with benzimidazole derivatives tend to possess some vitamin activity for animals while those containing purines tend to have activity only for micro-organisms². The relative activities vary with different micro-organisms and even with the particular assay technique used³. In rumen contents, vitamin B₁₂ itself makes up about 10 per cent of the activity for Escherichia coli, factor A (containing 2-methyl adenine) composes about 60 per cent, while pseudo-vitamin B₁₂ (containing adenine), factor B (containing no nucleotide) and factor C (containing guanine) account for most of the remainder⁴. Relatively little work has been reported in regard to the part played in the synthesis of these compounds by the individual species of micro-organisms obtained from the rumen and in general such studies have not included true or functional rumen organisms⁵.