Enrichment of Auxotrophic Mutants in Streptomyces griseus.

A method for the isolation and enrichment of tryptophan auxotrophic mutants of the indolmycin-producing strain Streptomyces griseus ATCC 12648 was developed, using penicillin selection. With UV irradiation of 2.2 x 10 muW cm, a mutation rate to tryptophan auxotrophy of 5.6 x 10 was achieved. With 300 mug ml of penicillin G, an enrichment of tryptophan auxotrophs of about 1,000-fold was attained. Approximately 40% of all survivors were tryptophan auxotrophs.