Summary: sp. strain C5, an organism that normally produces baumycins, daunomycin and ɛ-rhodomycinone, was treaed with N-methyl-N'-nitro-N-nitrosoguanidine (NTG). Mutants blocked at arious points in daunomycin and baumycin production were isolated by screening for altered pigmentation and absnce of bioactivity against . Examination of the mutants by thin-layer chromatography of their accumulated anthracycline metabolites, by cosynthesis assays, and by extract feeding experiments allowed a classification into six groups. Theses were: , strains that accumulated no anthracyclines but with other blocked mutants cosynthesized anthracyclines (polyketide-synthase-minus mutants); , regulatory mutants that, either alone or mixed with other blocked mutants, accumulated no anthracyclines; , mutants that accumulated aklanonic acid; , mutants that accumulated maggiemycin; , mutants that accumulated aklavinone; and , mutants that accumulated only ɛ-rhodomycinone. Mutant SC5-24 (), which accumulated that shunt product maggiemycin, was re-mutagenized with NTG to obtain blocked mutants in preceding biosynthetic steps; the three grops of double mutants obtained accumulated aklanonic acid (), aklanonic acid methyl ester () and akalviketone ().


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