An explanation for the apparent host specificity of Pseudomonas plasmid R91 expression

Publisher Website
Google Scholar
Abstract
P. aeruginosa strain 9169 contained a plasmid that expresses resistance to carbenicillin (Cb), kanamycin (Km) and tetracycline (Tc) in Escherichia coli but resistance only to Cb in certain Pseudomonas recipients. The triply resistant plasmid in E. coli belonged to incompatibility (Inc) group P or P-1, but the singly resistant plasmid in P. aeruginosa was compatible with IncP-1 plasmids and other plasmids of established Inc specificity but incompatible with plasmid pSR1 that is used to define a new Pseudomonas Inc group P-10. Additional physical and genetic studies showed that strain 9169 contained not 1 but 2 plasmids: IncP-1 plasmid R91a, determining the Cb Km Tc phenotype, and IncP-10 plasmid R91, determining Cb that differed in MW and in EcoRI and BamHI restriction endonuclease recognition sites. Plasmid multiplicity rather than host effects on plasmid gene expression can account for differences in the phenotype of strain 9169 transconjugants to E. coli and P. aeruginosa.