Anguibactin- versus vanchrobactin-mediated iron uptake in Vibrio anguillarum: evolution and ecology of a fish pathogen.

Vibrio anguillarum is a marine bacterium that is present in many marine aquatic environments and that is the main cause of vibriosis in diverse wild and cultured fish species. Two siderophore-mediated iron uptake systems have been described in V. anguillarum. One, mediated by the siderophore anguibactin, is encoded by the pJM1-type plasmids and is restricted to serotype O1 strains. The second one is mediated by the vanchrobactin siderophore and is widespread in many strains belonging to different serotypes. Both siderophores belong to the catecholate group of siderophores, sharing a 2,3-dihydroxybenzoic acid moiety. Vanchrobactin biosynthesis and transport genes are present in all strains examined although the siderophore is not produced in serotype O1 strains harbouring a pJM1-type plasmid. In these strains the insertion of an IS element in the main vanchrobactin biosynthetic gene vabF leads to the fact that only anguibactin is produced. From our current knowledge we can presume that vanchrobactin is the ancestral siderophore in this species and that the anguibactin-mediated system was later acquired during evolution, likely by horizontal transfer. The role of these two different iron uptake mechanisms in the biology, evolution and ecology of V. anguillarum is discussed although they are still far from being completely understood.