Recombination between the plasmid prophages P1 and P7 and the E. coli chromosome.

The prophages of the related temperate phages P1 and P7, which normally exist as plasmid DNA, suppress E. coli dnaA(Ts) by integrating into the host chromosome. Integratively suppressed strains may either be capable of producing phage or may have prophage deletions. In strains containing non-defective prophages, the location of the site on the prophage used for integrative recombination was identified by use of restriction analysis and DNA-DNA hybridization techniques. At least seven different integration sites were found on the prophage; the site used most often may be at the 'end' of the genetic map generated by vegetative phage crosses. For suppression of P1 and P7, the sites on the host chromosome utilized for prophage integration are not distributed randomly.