The Streptomyces aureofaciens plasmid pIMB R8 and its use for shuttle vector construction.

The cryptic low copy plasmid designated as pIMB R8 was isolated from an industrial strain of the chlortetracycline producer Streptomyces aureofaciens R8/26. Using restriction endonucleases the pIMB R8 plasmid was characterized to have 15 kb. Subcloning of the Bam HI fragments of pIMB R8 into replication probe vector resulted in the identification of the replication part. The 0.7 kb Bc/I--Bg/I fragment is sufficient for normal replication, but produces about fourty times high plasmid copy numbers than the original pIMB R8. Using the replication part of pIMB R8 was constructed several shuttle cloning vectors for the E. coli-streptomycete system.