Genetische Rekombination in Mutanten des Anthracyclin‐Bildners Streptomyces griseus

It was found that genetic recombination occurs if two marked strains of Streptomyces griseus (leukaemomycin‐producing strains. IMET JA 3933 and IMET JA 5142) are grown together in mixed cultures on semisolid media. The crossing techniques used and the method for carrying out selective analysis were essentially the same as those described by HOPWOOD (1967, 1972). The parent strains used for crosses were marked with single or double nutritional requirements and with mutations for drug resistance. The crosses are quite self‐sterile, yielding only in one combination stable prototrophic recombinants at a low frequency (10 −5 to 10 −6 ). The majority of recombinants behaved as stable haploid genotypes. A series of four‐point crosses of different types of auxotrophs was carried out. The results of these experiments do not provide sufficient data for constructing a chromosome map, but provide basic information on the possibilities of genetic analysis of the production of anthracycline antibiotics. The majority of crosses performed were not fertile at 28°C but, surprisingly, in some crosses carried out at 34°C viable colonies were detected on minimal media at frequencies from 10 −3 to 10 −2 .