Development of cloning vehicles from the Streptomyces plasmid pFJ103.

A 20-kb plasmid, pFJ103, was isolated from a strain of Streptomyces granuloruber. A restriction endonuclease map of the plasmid was constructed. A Streptomyces gene that specifies resistance to the antibiotic thiostrepton was subcloned into Escherichia coli plasmid pBR322, inserted into pFJ103 and transformed into Streptomyces ambofaciens protoplasts. Two classes of transformants were obtained. One carries the pFJ104 plasmid consisting of the entire pFJ103 with the 1.8-kb thiostrepton resistance gene insert. The other carries the pFJ105 plasmid consisting of the 2.9-kb replicon segment of pFJ103 with the same thiostrepton resistance insert. A gene for neomycin resistance together with the entire E. coli pBR322 plasmid were cloned into pFJ105. The resulting E. coli-Streptomyces bifunctional vector, pFJ123, transformed both E. coli and Streptomyces. The small size of pFJ105, its ease of isolation, and efficient transformation of Streptomyces protoplasts establishes it, and its derivatives, as useful plasmid cloning vehicles for fundamental and applied studies.