Plasmid-mediated iron uptake and virulence in Vibrio anguillarum.

The plasmid pJM1 of Vibrio anguillarum harbors genes encoding proteins that enable the bacterial cell to survive under iron limiting conditions. A subset of these proteins are involved in the biosynthesis of the siderophore anguibactin and in the internalization of the ferric-siderophore into the cell cytosol. We have identified several genes encoding non-ribosomal peptide synthetases that catalyze the synthesis of anguibactin, these genes are: angB/G, angM, angN, angR, and angT. In addition, the genes fatA, fatB, fatC, and fatD are involved in the transport of ferric-anguibactin complexes. These transport genes, together with the biosynthesis genes angR and angT, are included in the iron transport biosynthesis operon (ITBO). Both the biosynthesis and the transport genes are under tight positive as well as negative control. We have identified four regulators; two of them, a chromosomally encoded Fur and a plasmid-mediated antisense RNA, RNAbeta, act in a negative fashion, while positive regulation is facilitated by AngR and TAFr. We also have evidence that the siderophore itself plays a positive role in the regulatory mechanism of the expression of both transport and biosynthesis genes.