Patterns of Mobilization of the Proteus mirabilis Chromosome by R Plasmids

Abstract

R plasmids R40a, Rip69, R447b, R769 belonging to incompatibility groups A-C, M, N, V, respectively, were investigated for chromosomal mobilizing ability in P. mirabilis. Plasmids R40a, Rip69 and R447b mediated polarized transfer of markers in a clockwise direction from origins near tyr-1, metF and ser-2, respectively, on the linkage map. The recovery frequency per donor cell of proximal markers approached 1 .times. 10-4 for these 3 plasmids and the efficiency of chromosomal transfer was higher than that of the previously studied plasmid D. The plasmid-guided chromosomal trajectories overlap and it was possible to complement results obtained with plasmid D to assemble a time-of-entry chromosomal map and directly establish the circularity of the linkage group. The map comprises a length of 93 min in terms of transfer time. Plasmid R769 had a different pattern of chromosome transfer. This plasmid produced recombinants for all markers at frequencies of about 4 .times. 10-6/donor. It effected multiple and more or less simultaneous entry of markers and produced recombination over lengths of chromosome rarely corresponding to more than 10 min on the linkage map.