Comparative sequence analysis of plasmids in Vibrio anguillarum serovar O1 strains from different geographic locations and fish species

The genetic diversity of Vibrio anguillarum 65 kb 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 a ~65 kb plasmid like the PJM1 plasmid and all plasmids encoded the majority of the virulence genes responsible for the anguibactin iron sequestering system. The plasmids were highly conserved but minor differences were observed in some genes. Single nucleotide variations (SNVs) analysis showed 0 to 11 nucleotide variations between each of the 18 plasmids and the pJM1 plasmid. Compared to the sequence of pJM1, non-synonymous SNVs 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 geographical origin or fish species.