The anguibactin biosynthesis and transport genes are encoded in the chromosome of V ibrio harveyi : a possible evolutionary origin for the p JM 1 plasmid–encoded system of V ibrio anguillarum ?

Many V ibrio anguillarum serotype O 1 strains carry 65‐kb p JM 1‐type plasmids harboring genes involved in siderophore anguibactin biosynthesis and transport. The anguibactin system is an essential factor for V . anguillarum to survive under iron‐limiting conditions, and as a consequence, it is a very important virulence factor of this bacterium. Our comparative analysis of genomic data identified a cluster harboring homologs of anguibactin biosynthesis and transport genes in the chromosome of V ibrio harveyi . We have purified the putative anguibactin siderophore and demonstrated that it is indeed anguibactin by mass spectrometry and specific bioassays. Furthermore, we characterized two genes, angR and fatA , in this chromosome cluster that, respectively, participate in anguibactin biosynthesis and transport as determined by mutagenesis analysis. Furthermore, we found that the V . harveyi FatA protein is located in the outer membrane fractions as previously demonstrated in V . anguillarum . Based on our data, we propose that the anguibactin biosynthesis and transport cluster in the V . anguillarum p JM 1 plasmid have likely evolved from the chromosome cluster of V . harveyi or vice versa.