Unstable Naturally Occurring Resistance to Antibiotics in Streptomyces

Two sets of observations suggested that extrachromosomal elements conferring antibiotic resistance might be widespread in streptomycetes. One was the evidence for plasmids affect-ing various other phenotypic properties in these organisms. Streptomyces coelicolor ~ 3 ( 2) contains a plasmid, SCPl, which acts as a conjugal sex factor and also codes for methyl-enomycin production and resistance (Kirby, Wright & Hopwood, 1975; Wright & Hopwood, 1976); less direct evidence implicates plasmids in the control of antibiotic production in Streptomyces kasugaensis (Okanishi, Ohta & Umezawa, 1970), Streptomyces hygroscopicus (Kahler & Noack, 1974) and Streptomyces venezuelae (Akagawa, Okanishi &amp