[Reduction of actinomycin biosynthesis during protoplast regeneration in an inactive variant producer]

During regeneration of protoplasts in the inactive variant H-2 of the actinomycin-producing organism Streptomyces sp. 26-115 there were detected 1-4 per cent of the colonies synthesizing the antibiotic. The frequency of such colonies (H-2R) did not increase after exposure of the H-2 protoplasts to the fusing agent PEG-1000. The population grown from one colony after three passages on pea agar was sufficiently homogeneous by the antibiotic production property. Variant H-2R was more stable to the effect of streptomycin than the initial variant H-2.