CONVERSION OF D-BIOTIN TO BIOTIN VITAMERS BY LACTOBACILLUS ARABINOSUS.

Birnbaum, Jerome (University of Cincinnati College of Medicine, Cincinnati, Ohio), and Herman C. Lichstein. Conversion of d-biotin to biotin vitamers by Lactobacillus arabinosus. J. Bacteriol. 89:1035-1040. 1965.-Saccharomyces cerevisiae utilizes d-biotin, biotin sulfoxide, and several vitamers of biotin, whereas Lactobacillus arabinosus responds to biotin and biotin sulfoxide of the naturally occurring forms of the vitamin. The use of these organisms for differential assay permitted investigation into possible conversion of d-biotin to vitamers of biotin by cells of L. arabinosus. Cells were grown in modified Wright-Skeggs medium containing several levels of biotin. No differences were detected between the assays for free intracellular or bound biotin up to 48 hr of growth. However, at 15 to 16 hr, in media containing an excess of biotin, the lactobacillus assay value for menstruum biotin dropped markedly, whereas the yeast assay showed no change. This suggested that biotin was converted to vitamers not active for L. arabinosus. The biotin-converting system appears to have characteristics of an enzyme system, i.e., a temperature optimum at 37 C, a broad pH optimum of 4.3 to 6.5, and requirements for Mg and Mn ions. Experiments suggest that increasing hydrogen ion concentration is a major physiological mechanism controlling the formation of this system. The vitamers were separated chromatographically and were found to have R(F) values of 0.44 and 0.94, and are combinable and uncombinable with avidin, respectively. The physiological role of biotin conversion is discussed in relation to control of cell populations in cultures of L. arabinosus.