Distribution of three genes involved in the PJM1 iron-sequestering system in various Vibrio anguillarum serogroups

Gene sequences with high homologies to the two genes fatA and fatD, associated with the pJM1 virulence plasmid-encoded iron-sequestering system (anguibactin) in Vibrio anguillarum serogroup O1 strains, were found in a range of serogroup O2a strains and one NT 4 strain that either contained no plasmids or only small-sized plasmids. None of these strains contained the angR gene responsible for regulation of the anguibactin synthesis. DNA sequences of presumed fatA and fatD fragments from one O2a strain and one NT4 strain were identical to each other. The fatA sequence of these strains included 35 nucleotide substitutions and 7 amino acid substitutions out of 555 nucleotides when compared with the fatA sequence of the O1 strain 76 775. The fatD sequence included 10 nucleotide substitutions and 1 amino acid substitution out of 543 nucleotides when compared with 76 775. The fact that the majority of nucleotide substitutes in the fatA and fatD fragments did not result in amino acid substitutes suggest that these sequences may to some degree be preserved by selective pressure. The functional role of these genes in the O2a serogroup is most likely different from their role in the pJM1 system.