Factors affecting the conjugal proficiency of Pseudomonas aeruginosa

R68 is a wide host-range plasmid of 36 x 1ø⁶ daltons that codes for resistance to several antibiotics. R68.45 is a derivative of R68 which contains a 1.5 Mdal insertion of DNA which enables it to mobilize the chromosome of a wide variety of gram-negative organisms. Maps of these plasmids have been constructed by analysis of DNA fragments produced by cleavage with ten restriction endonucleases singly and in combination. Positions of the enzyme recognition sites were assigned relative to the single EcoRI site. The restriction map of R68 appears to be identical to those of RPl and RK2. The 1.5 Mdal DNA insertion in R68.45 is located between the SalI-HindIII region of the map and was found to contain additional restriction sites for the enzymes Hpal, PstI, PvuII, and Smal.

R68 and R68.45 were also used in the study of P. Aeruginosa mutants with an impaired ability to be lysogenized by several temperate bacteriophages (Les-). I have examined the effects of several les mutations on the maintenance and conjugal efficiency of R68 and R68.45 in addition to the fertility factors FP2, FP5, FP11ø::TN7

Plasmid transfer and recombinant formation were measured using parental and les containing strains as both donors and recipients in conjugations mediated by the various sex factors. The results indicate the existence of two phenotypic classes with respect to the ability of the Les- strains to act as recipients of plasmid DNA. Effects on the ability to donate plasmid and chromosomal DNA were found to be both plasmid and strain specific.

The maintenance of the various fertility factors in the Les- strains were tested and found to be significantly decreased in the Les-, Rec- strains RM8 and RM231.

There is evidence that the sex factor FP2 carries a suppressor of les. I have tested 21 plasmids from 10 different incompatibility groups for any similar ability to suppress this phenotype. In addition to FP2, the R factors R2, Rms148 and Rms163 were found to have this property.