Isolation and characterization of furanomycin nonproducing Streptomyces threomyceticus mutants

Stable mutants that are blocked in the production of the polyketide antibiotic furanomycin were generated by treatment of Streptomyces threomyceticus (ATCC 15795) with a combination of N-methyl-N'-nitro-N-nitrosoguanidine (NTG) and ultraviolet light. On the basis of their cosynthetic properties in mixed culture, the mutants were grouped into eleven phenotypic classes. The polarity of the cosynthetic reactions for seven classes of mutants was revealed by filtrate feeding experiments. This allowed them to be arranged in the most probable linear sequence of metabolic blocks. One of the remaining groups of mutants exhibited no cosynthetic behavior and is believed to be blocked in a gene that regulates furanomycin biosynthesis.