ParI , an orphan ParA family protein from P seudomonas putida KT 2440‐specific genomic island, interferes with the partition system of IncP ‐7 plasmids

Abstract

Summary P seudomonas putida KT 2440 is an ideal soil bacterium for expanding the range of degradable compounds via the recruitment of various catabolic plasmids. In the course of our investigation of the host range of IncP ‐7 catabolic plasmids pCAR 1, pDK 1 and pWW 53, we found that the IncP ‐7 miniplasmids composed of replication and partition loci were exceptionally unstable in KT 2440, which is the authentic host of the archetypal IncP ‐9 plasmid pWW 0. This study identified ParI , a homologue of ParA family of plasmid partitioning proteins encoded on the KT 2440‐specific cryptic genomic island, as a negative host factor for the maintenance of IncP ‐7 plasmids. The miniplasmids were destabilized by ectopic expression of ParI , and the loss rate correlated with the copy number of ParB binding sites in the centromeric parS region. Mutations in the conserved ATP ase domains of ParI abolished destabilization of miniplasmids. Furthermore, ParI destabilized miniplasmid derivatives carrying the partition‐deficient parA mutations but failed to impact the stability of miniplasmid derivatives with parB mutations in the putative arginine finger. Altogether, these results indicate that ParI interferes with the IncP ‐7 plasmid partition system. This study extends canonical partition‐mediated incompatibility of plasmids beyond heterogeneous mobile genetic elements, namely incompatibility between plasmid and genomic island.

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