[Properties of potential vectors--derivatives of the broad-host--range plasmid RP4].

Nonconjugative deletion and recombinant derivatives of the RP4 plasmid are constructed. The plasmids can be used as vectors because they have relatively small molecular weights, unique cleavage sites for enzymes EcoRI, XhoI, BamHI, PstI, KpnI, BglII, SalGI and HindIII (the plasmids pRP401 and pRP417 having six of these sites), and easily tested phenotypes (Tcr, Apr and Gal+). In addition, all of them retain the broad host range property. Also, the plasmid pRP420 is a multicopy derivative capable of amplification. The plasmids are mobilized by conjugative plasmids pRK2013 and Flac from Escherichia coli cells into Rhizobium meliloti and Pseudomonas aeruginosa strains. Flac-mediated mobilization of the pRP417 plasmid which has an internal deletion of the transposon Tn1, is decreased, in comparison with the nondeleted plasmid. ColE1 replication machinery is inhibited for RP4--ColE1 recombinant derivatives, if both components are joined via EcoRI restriction site. This inhibition does not depend on the orientation of joined molecules. ColE1 replication machinery is functional, if delta RP4 and ColE1-like plasmids are joined via PstI cleavage site.