In vitro insertion of the lambda attachment site into the plasmid RP4.

The region of the phage lambda chromosome containing the attachment site (P.P') and the genes int and xis, excised by the action of endonuclease R.EcoRI, has been inserted into the unique site for that enzyme on the promiscuous conjugative plasmid, RP4, generating the recombinant plasmid RP4att lambda. Transformants containing the hybrid plasmid were recognised by their ability to allow efficient lysogenization by phage lambda b2 (Weil and Signer, 1968; Echols et al., 1968) containing the mutant attachment site delta. P'. The construction and properties of the hybrid plasmid RP4att lambda are described.