Sequence Analysis of Plasmids in Vibrio anguillarum from Different Fish and Locations

The genetic diversity of Vibrio anguillarum pJM1-like plasmids was investigated. Plasmids were isolated from 18 V. anguillarum serovar O1 strains collected from different geographic locations and fish species. The plasmids were sequenced and compared with the complete sequence of the published virulence plasmid pJM1. All 18 strains contained pJM1-like plasmids with approximately 65 kbp and all plasmids encoded the virulence genes responsible for the anguibactin iron sequestering system. The plasmids were highly conserved but minor differences were observed in some genes. A single nucleotide polymorphisms (SNPs) analysis showed 0-11 nucleotide variations between each of the 18 plasmids and the pJM1 plasmid. Compared with the sequence of pJM1, nonsynonymous SNPs were identified in fatC, angR, angL, pJM1_p19, and angE. In particular, a mutation found in 15 out of 18 sequenced plasmids in angR has previously been linked to hyperproduction of anguibactin and was found in all the European isolates. However, overall the pJM1-like plasmids isolated from V. anguillarum serovar O1 exhibited a high degree of conservation regardless of their geographical origin or fish species.