Genetic characterization of pPHDP60, a novel conjugative plasmid from the marine fish pathogen Photobacterium damselae subsp. piscicida

A new plasmid designated pPHDP60 from a strain of the marine bacterium Photobacterium damselae subsp. piscicida isolated from diseased seabream has been characterised. pPHDP60 consists of 59,731 bp, has a G + C content of 37.2% and encodes 63 predicted open-reading frames (ORFs). The plasmid backbone sequence includes, among other genes, 15 ORFs homologous to proteins of type IV conjugation systems described in IncP-type plasmids. Two modules could be distinguished within pPHDP60 sequence. One module included 10 genes of a putative type II secretion system with homologues in other Photobacterium and Vibrio plasmids. A second module exhibiting a transposon structure included a functional haloalkane dehalogenase gene linB as well as a toxin/antitoxin system. Additional interesting features of pPHDP60 include its ability to be conjugally transferred to several Gram negative bacteria.

► pPHDP60 is a conjugative plasmid.
► pPHDP60 gene linB encodes an haloalkane dehalogenase.
► pPHDP60 harbours a gene cluster of a putative type II secretion system.