Isolation of Streptomycin-producing Strains of Streptomyces griseus

Abstract

Attempts were made to isolate new streptomycin-producing strains of S. griseus and to purify active strains by the use of a streptomycin-enriched medium. Inactive strains of S. griseus and other spp. of actinomycetes were found to be sensitive to streptomycin. A new active strain of S. griseus was isolated from a manured soil on a streptomycin-enriched medium. Several new strains of S. griseus which produced antibiotics that were found to be not of the streptomycin type were obtained. Streptomycin-producing strains of S. griseus form active and inactive variants; the inactive vari-ants comprised 2 types, one being free from aerial mycelium and the other producing an atypical pink tinge in the vegetative mycelium, the aerial mycelium being typical of S. griseus. Superior strains of S. griseus were not obtained, but it was established that the production of streptomycin is associated with a certain few strains of S. griseus, that these strains may continuously form inactive substrains, that a streptomycin-enriched medium may be utilized to purify active cultures of 5. griseus from inactive variants and that active strains may be isolated from natural substrates on streptomycin-enriched medium.