Effect of B-factor and its analogues on rifamycin biosynthesis in Nocardia sp.

B-Factor, 3'-(1-butylphosphoryl)adenosine, which was isolated from yeast extract, is an inducer of rifamycin production in a rifamycin non-producing Nocardia mutant. Feeding of B-factor to the mutant culture demonstrated that the induction process was triggered during early stationary phase. Rifamycin production in the mutant was also induced by an exogenous supply of 3-amino-5-hydroxybenzoic acid, an intermediate of the antibiotic pathway, suggesting that a step upstream from the intermediate is regulated by B-factor. B-Factor analogues, i.e., alkylesters of 3'-AMP with alkyl side chains of C(2) approximately C(12) and n-butyl esters of 3'-GMP and 2'-AMP all showed the B-factor activity. Among these n-octyl ester of 3'-AMP showed the lowest effective concentration of approximately 3 x 10(-10) M. An intrinsic substance of the Nocardia sp. with potent B-factor activity and a UV absorption maximum at 260 nm was isolated from the cells of the parental strain.