The Active Partition GeneincCof IncP Plasmids Is Required for Stable Maintenance in a Broad Range of Hosts

Open Access
Publisher Website
Google Scholar
Abstract
Plasmids of incompatibility group P (IncP) are capable of replication and stable inheritance in a wide variety of gram-negative bacteria. Three determinants of IncP plasmids are components of an active partition locus that is predicted to function in the segregation of plasmid copies to daughter cells. These determinants areincC, which codes for a member of the ParA family of partition ATPases;korB, which specifies a DNA-binding protein that also functions as a global transcriptional repressor; and OB, the DNA target for KorB, which occurs at multiple locations on IncP plasmids. To determine the importance and host range of the IncC/KorB partition system in the maintenance of IncP plasmids, we constructed an in-frame deletion ofincCin the otherwise intact 60-kb IncPα plasmid R995. R995ΔincCwas found to be highly unstable inEscherichia coli, Pseudomonas aeruginosa, Pseudomonas putida, Agrobacterium tumefaciens, andAcinetobacter calcoaceticus, whereas wild-type R995 is stable in all these hosts. In addition, R995ΔincCcould not be established inActinobacillus actinomycetemcomitans.trans-Complementation analysis showed that the coding region for IncC2 polypeptide, which is expressed from an internal translational start within theincCgene, was sufficient to restore stable maintenance to wild-type levels. The results show that the IncC/KorB active partition system of IncP plasmids is remarkably proficient for stable maintenance in diverse bacteria.