Characterization of Pseudomonas aeruginosa derepressed R-plasmids

Publisher Website
Google Scholar
Abstract
A genetic study of conjugal transmissibility of 2 R-plasmids was undertaken in P. aeruginosa. Conjugally derepressed mutants of the R-plasmids were isolated, and examination of 11 independent mutants revealed that 10 were recessive to the wild-type transfer repressor, but 1 mutant was cis dominant. Cross-repression was observed between the 2 R-plasmids, suggesting that they have functionally equivalent systems for regulating the expression of tra loci. The derepressed R-plasmid mutants exhibited several characteristics, in addition to derepressed transfer, that were not expressed by the parental plasmids. These included sensitivity to certain donor-specific phages, inhibition of multiplication of a transducing phage, and in the 1 case examined, a high degree of entry exclusion. The coexpression of these different functions suggests that their respective genetic loci are controlled by the same regulatory system as that of tra or that they are part of the tra complex.