Genetic Determination of Methylenomycin Synthesis by the SCPl Plasmid of

Evidence is presented that genes determining the pathway of methylenomycin A synthesis are carried on the SCPI plasmid. All 16 mutations (mmy) leading to lack of antibiotic synthesis were SCPI -linked. Phenotypic classification, by co-synthesis and other criteria, suggested that they fell into at least five classes. When the wild-type SCP I plasmid was transferred to Streptomyces lividans or Streptomyces parvulus, material that was chromatographically and biologically indistinguishable from methylenomycin A was produced. Recombination between some pairs of mrny mutations was detected. In crosses of mmy mutants of NF (integrated SCPI donor) strains with SCPI-, a very high frequency of chromosomal recombination occurred; thus methylenomycin production appears not to be an important cause of the ultra-fertility normally associated with NF x SCPIcrosses.