A gene cluster involved in the biosynthesis of vanchrobactin, a chromosome-encoded siderophore produced by Vibrio anguillarum

Abstract

Vibrio anguillarumserotype O2 strains produce a catechol siderophore named vanchrobactin, which has been identified asN-[N′-(2,3-dihydroxybenzoyl)-arginyl]-serine. This work describes a chromosomal region that harbours the genetic determinants necessary for the biosynthesis of vanchrobactin. The authors have identified the genes involved in 2,3-dihydroxybenzoic acid (DHBA) biosynthesis (vabA,vabBandvabC) and activation (vabE), and a gene (vabF) encoding a non-ribosomal peptide synthetase, which is putatively involved in the assembly of the siderophore components. Also described are the identification and characterization of genes encoding a putative vanchrobactin exporter (vabS) and a siderophore esterase (vabH). In-frame deletion mutants invabA,vabB,vabC,vabE,vabFandvabHwere impaired for growth under conditions of iron limitation, and the analysis of culture supernatants by chrome azurol-S and cross-feeding assays showed almost no production of siderophores in any of thevabABCEFmutants. In addition, deletion mutations ofvabA,vabBandvabCabolished production of DHBA, as assessed by chemical and biological analyses. Complementation of each mutant with the corresponding gene providedin transconfirmed the involvement of this gene cluster in the biosynthesis of DHBA and vanchrobactin inV. anguillarumstrain RV22. Based on chemical and genetic data, and on published models for other catechol siderophores, a model for vanchrobactin biosynthesis is proposed.