Phylogenetic relationships among Vibrio anguillarum plasmids.

Results of restriction endonuclease analysis and Southern blot hybridization suggest that the R-plasmids from Vibrio anguillarum strains isolated in Japan can be divided into at least four groups of homology depending on the time of their isolation and geographical source. Molecular cloning experiments allowed identification of specific restriction endonuclease fragments carrying the genes for either Cmr or Tcr as the common sequences between some of these groups of R-plasmids. The Cmr region from the V. anguillarum R-plasmids was homologous to the Cmr sequences of an R-plasmid isolated from another fish pathogen, Aeromonas salmonicida. The plasmid pJM1 from V. anguillarum strains isolated in the Pacific Northwest region of the United States, which encodes an iron transport system associated with the high-virulence phenotype of these strains, showed homology with two of the Japanese R-plasmids.