[The isolation and characteristics of mutant Streptomyces globisporus 1912 defective for landomycin E biosynthesis].

Mutants defective in the synthesis of antitumor angucycline antibiotic landomycin E were obtained from the asporogenic and initial sporulating strains of Streptomyces globisporus 1912 by means of nitrosoguanidine treatment and UV-irradiation of the mycelium fragments and protoplasts. The frequency of induction of LanE mutants in the protoplasts of strain 3-1 was 3 times higher (0.55%) as compared to mycelium fragments (0.17%). After mutagenic treatment of spores the yield of such mutants was lower (0.044-0.071%). It was shown, that izoflavon daidzein was an effective and necessary regulator of the landomycin E synthesis. The collection of 53 landomycin defective mutants was divided into three groups on the basis of their ability to produce antibiotic and regulator: 1) mutants LanE-Dai+ (45 strains), which did not synthesize landomycin E, but produced daidzein; 2) mutants LanE+Dai- (4 strains), which could restore landomycin E synthesis after adding exogenic daidzein to the medium and 3) mutants LanE- Dai- which did not synthesize landomycin E in the presence of daidzein.