Construction and characterization of a cosmid of Streptomyces lividans

We constructed a plasmid pR4C1 in which a DNA fragment containing the cohesive ends of an actinophage, R4 was inserted into the ClaI site of plasmid pIJ365. The plasmid pR4C1 was packaged efficiently into R4 phage particles in vivo and therefore transferred by transduction. Southern hybridization analysis of DNA from pR4C1-transducing R4 phage particles indicated that the plasmid DNA was encapsidated as head-to-tail concatemers with the cohesive ends in the termini. We designated the pR4C1 plasmid a cosmid, following the termination of Collins and Hohn (1978).