IMPROVEMENT IN STREPTOMYCIN-PRODUCING STRAINS OF STREPTOMYCES GRISEUS BY ULTRAVIOLET AND X-RAY ENERGY

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Abstract
S. griseus (Waksman''s no. 4) was irradiated by both u.-v. and X-rays in an effort to produce high-streptomycin-yielding strains. X-rays were found to be much more mutagenic than u,-v., and among X-rays, the harder rays of 0.71 A. and 0.21 A wave lengths were found to be the most efficient mutagens. Mutation rate increased with killing rates up to 99.9% killing. By using doses up to 1,000,000 r., mutation rates as high as 50% were observed on morph. characteristics, and as high as 40% on the single physiol. characteristic of streptomycin production. The superior strains selected proved to be extremely unstable and quickly reverted to the parent type, insofar as streptomycin production was concerned. Less than 0.1%, 3 out of 3700 strains studied, proved to be superior in a stable fashion. Strain superiority is very dependent upon the medium being fermented. Strains have been produced which give yields of 700-900 [mu]g./ml. of streptomycin on the proper medium.