Vitamin B₁₂-controlled Biotin Avidity in Autotrophic Euglena gracilis

Abstract

SEVERAL years ago, it was found that colls from recently isolated but impure (0.1 per cent contaminants) cultures of the autotrophic bacterium Nitrosomonas europeae contained more than 10 µg biotin/g dried cells¹. Because such values are considerably higher than the 1.7–7.1 µg biotin per g of dried cells reported for five species of heterotrophic bacteria², we suggested that autotrophs might require large amounts of biotin for utilization of their carbon source, carbon dioxide. Assay of biotin content of pure cultures of autotrophic bacteria revealed that they contained the same amount or only slightly less biotin than do heterographs: N. europeae contained 1.6–2.4 µg and Nitrobacter agilis contained 0.56–1.0 µg biotin/g dried cells³.