In vitro-constructed RP4-prime plasmids mediate orientated mobilization of the Proteus morganii chromosome.

RP4-prime plasmids containing inserts of Proteus morganii strain 2815 chromosomal DNA (0.5-13 megadaltons in size) were constructed in vitro. When introduced into the latter organism, the hybrid plasmids promoted transfer of chromosomal markers in an orientated manner, with recombinant frequencies from 10(-4) to 10(-6) per donor. Transconjugants expressed the tetracycline-resistant phenotype of the plasmids. Plasmid-guided trajectories overlapped and a circular map of chromosome markers was constructed. Correspondence between size of inserted chromosomal DNA in hybrid plasmids and numbers of markers transferred suggested that homology played a role in chromosome mobilization by these plasmids.