[Operon of riboflavin synthesis in Bacillus subtilis. IX. Preparation and properties of lumiflavin- or lumichrome-resistant mutants].

Lumiflavin and lumichrome both inhibit the growth of different strains of Bacillus subtilis including riboflavin-constitutive mutant. Lumiflavin has no regulating effect, but lumichrome is an effector and it participates in the repression of riboflavin precursors synthesis and the synthesis of riboflavinsynthetase. Mutants resistant to lumiflavin or lumichrome accumulate a mixture of riboflavin, FMN and FAD. Their regulatory characteristics are substantially altered. They are repressed by higher concentrations of all effectors comparing with the wild type. The mapping of resistant mutants showed that the most of them are located near to ribC gene, probably inside of it. The simultaneous presence of all three flavins in the cultural medium shows that the regulatory protein is universal to the biosynthesis of all flavins.