Mutation in Streptomyces flaveolus Induced by X-rays and Ultraviolet Light

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Abstract
S. flaveolus ATCC 3319 was irradiated with u.-v. light and with X-rays in order to determine quantitatively the effect of these agents on the mutation frequency of this organism. The most common types of morphological mutants were "yellow," a pigmented form resembling Bergey''s description of S. flaveolus more closely than the ATCC culture; "asporogenous," in which aerial spores were absent; and "restricted" strains growing poorly on asparagine glucose agar. U.-v. irradiation doses up to 20,000 ergs X mm-2 were studied. Results were variable, but in all cases mutation frequency rose steadily with dose, with no evidence of a falling off of the rate of increase at large doses. Doses of X-rays up to 300,000 r were studied. Mutation frequency rose with dosage up until about 200,000 r, above which the rate of increase leveled off. Since results with X-rays were more uniform than with u.-v. light, it is the preferred agent for inducing mutation in actinomycetes.