Construction and some properties of packageable plasmid F

Abstract

A derivative of plasmid F which is packageable in lambda 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 beta-lactamase gene, and a portion of guaA (B) transducing lambda phage DNA carrying lambda 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 x 10(7) daltons, about 84% size of lambda phage genome, and can be packaged in lambda coat when helper phage replicates in the plasmid-carrier cell. The packaged plasmid and the helper lambda 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.