[Spontaneous and induced variability in Actinomyces rubiginosohelvolus, a new producer of the antibiotic rubomycin].

Mutants possessing 3 times higher activity as compared to the initial culture were obtained as a result of selection of active variants of Act. rubiginosonelvolus, a new organism producing rubomycin against the background of variation induced by N-methyl-N1-nitro-N-nitrozoguinidine, diethylsulphate and their combinations. Further selection among the mutants stable to 6-mercaptopurine and riboflavine resulted in obtaining an active culture No. 3912 at least 7 times more active with respect to rubomycin production than the initial soil culture.