CONSTRUCTION AND SOME PROPERTIES OF PACKAGEABLE PLASMID-F

A derivative of plasmid F which is packageable in λ phage coat was constructed using techniques of in vitro recombination. This plasmid is composed of three DNA fragments generated by restriction enzyme EcoRI: a miniF fragment (fragment f5 of F'lac) which is able to replicate autonomously, a DNA fragment from Staphylococcus Plasmid that carries the β-lactamase gene, and a portion of guaA (B) transducing λ phage DNA carrying λ cohesive ends (cos site) along with almost all the late genes but devoid of all those genes and sites that are needed for replication, regulation, and recombination. The hybrid plasmid has a molecular weight of 2.7×107 daltons, about 84% size of λ phage genome, and can be packaged in λ coat when helper phage replicates in the plasmid-carrier cell. The package plasmid and the helper λ phage particles are separated by CsCl density gradient centrifugation. The replication characteristics of the recombinant plasmid are all those of F including the copy number, incompatibility, and curing with acidine orange. The packaged plasmid is injected into an F- cell and establishes a plasmid state with normal efficiency. In F+ or Hfr cells, the resident F factor hinders this process. © 1979 Springer-Verlag.