Physical mapping shows that the unstable oxytetracycline gene cluster of Streptomyces rimosus lies close to one end of the linear chromosome

A restriction map of the 8 Mb linear chromosome of Streptomyces rimosus 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 DraI 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, which might account for its frequent spontaneous amplification and deletion. Several other markers were localized on the chromosome (dnaA and recA, the rrn operons, the attachment site for pSAM2 and prophages RP2 and RP3). Comparison of the conserved markers with the map of Streptomyces coelicolor A3(2) suggested there are differences in genome organization between the two species