PHYSICAL MAPPING SHOWS THAT THE UNSTABLE OXYTETRACYCLINE GENE-CLUSTEROF STREPTOMYCES-RIMOSUS LIES CLOSE TO ONE END OF THE LINEAR CHROMOSOME

A restriction map of the 8 Mb linear chromosome of Streptomyces rimosu s R6-501 was constructed for the enzymes AseI (13 fragments) and DraI (7 fragments). Linking clones for all 12 AseI sites and 5 of the 6 Dra I sites were isolated. The chromosome has terminal inverted repeats of 550 kb, which are the longest yet reported for a Streptomyces species . The oxytetracycline gene cluster lies about 600 kb from one end, whi ch might account for its frequent spontaneous amplification and deleti on. Several other markers were localized on the chromosome (dnaA and r ecA, the rm operons, the attachment site for pSAM2 and prophages RP2 a nd RP3). Comparison of the conserved markers with the map of Streptomy ces coelicolor A3(2) suggested there are differences in genome organiz ation between the two species.