FvtA Is the Receptor for the Siderophore Vanchrobactin inVibrio anguillarum: Utility as a Route of Entry for Vanchrobactin Analogues

Abstract

Some strains of Vibrio anguillarum, the causative agent of vibriosis in a variety of marine animals, produce a catechol-type siderophore named vanchrobactin. The biosynthetic pathway and regulation of vanchrobactin are quite well understood. However, aspects concerning its entry into the cell have remained uncharacterized. In the present study we characterized two genes, fvtA and orf13, encoding potential TonB-dependent ferricvanchrobactin receptors in serotype O2 V. anguillarum strain RV22. We found that an fvtA mutant was defective for growth under iron limitation conditions and for utilization of vanchrobactin, suggesting that fvtA encodes the vanchrobactin receptor of V. anguillarum. Interestingly, an orf13 mutant was not significantly affected, and results of reverse transcriptase PCR, as well as analysis of outer membrane proteins by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, suggested that this gene is not expressed. Furthermore, fatA, a plasmid gene coding for the anguibactin receptor in plasmid pJM1-harboring strains, is also present in the chromosome of RV22, although it is inactivated by insertion of transposases. In addition, we found that FvtA is the route of entry for vanchrobactin analogues, and there is evidence that it recognizes primarily the catechol-iron center. These analogues are potential candidate vectors for a Trojan horse strategy aimed at generating antimicrobial compounds exploiting the same route of entry for native siderophores. We found that fvtA and vanchrobactin biosynthesis genes are ubiquitous in both vanchrobactin-and anguibactin-producing V. anguillarum strains, which reinforces the utility of the vanchrobactin route of entry for the design of future strategies for the control of vibriosis.Vibrio anguillarum strains possess an array of specific virulence factors that enable them to cause a hemorrhagic septicemia called vibriosis in a variety of marine animals (41). There are more than 20 recognized serotypes, but serotypes O1 and O2 are the serotypes predominantly implicated in vibriosis outbreaks (43). Although the virulence mechanisms of V. anguillarum are not fully understood, it is known that the ability to scavenge iron through utilization of siderophores contributes significantly to the virulence of this bacterium (11,20,45). Currently, two clearly different siderophore-mediated iron uptake systems in V. anguillarum are known. One of them is the vanchrobactin-mediated system encoded by a chromosomal gene cluster. The chemical structure of the siderophore in this system and its biosynthesis and regulation pathways were recently established (3,4,36). The other system is a plasmid pJM1-encoded system called the anguibactin system that is found only in pJM1-containing serotype O1 strains (10, 40), whose synthesis requires additional chromosomal genes that are also involved in vanchrobactin production (1, 4).Uptake of ferric iron-siderophore complexes into the cell requires a specific outer membrane (OM) receptor protein connected to a TonB-ExbB-ExbD complex ...

Characterization of Vibrio parahaemolyticus genes encoding the systems for utilization of enterobactin as a xenosiderophore

“…The catecholate-type siderophore Ent is utilized as the iron source by several Gram-negative bacteria, including V. cholerae (Mey et al, 2002), V. anguillarum (Balado et al, 2009;Naka & Crosa, 2012), Pseudomonas aeruginosa (Dean & Poole, 1993;Ghysels et al, 2005), Neisseria gonorrhoeae (Carson et al, 1999), Bordetella species (Beall & Sanden, 1995) and Campylobacter species (Palyada et al, 2004;Xu et al, 2010). In this study, we also showed that V. .…”

“…Three sets of TonB systems, termed TonB1, TonB2 and TonB3, are present in this bacterium (Kuehl & Crosa, 2010), and the energy required for PvuA1 and PvuA2 to transport ferric vibrioferrin is provided by the TonB2 system, and both the TonB1 and TonB2 systems, respectively (Tanabe et al, 2011). In addition, V. parahaemolyticus can utilize hydroxamate-type xenosiderophores such as desferri-ferrichrome and aerobactin (Funahashi et al, 2003(Funahashi et al, , 2009 et al, 1986;Balado et al, 2009;Griffiths et al, 1984) and a xenosiderophore enterobactin (Ent) mainly produced by members of the family Enterobacteriaceae (Carson et al, 1999; Mey et al, 2002;Naka & Crosa, 2012; Stork et al, 2004;Wyckoff et al, 2007). However, to our knowledge, the ability of V. parahaemolyticus to utilize catecholate-type xenosiderophores has not yet been reported.…”

“…In addition, V. parahaemolyticus can utilize hydroxamate-type xenosiderophores such as desferri-ferrichrome and aerobactin (Funahashi et al, 2003(Funahashi et al, , 2009. Previous studies have demonstrated that several Vibrio species, including Vibrio cholerae and Vibrio anguillarum, can use catecholate-type siderophores, such as their cognate siderophores (Actis et al, 1986;Balado et al, 2009;Griffiths et al, 1984) and a xenosiderophore enterobactin (Ent) mainly produced by members of the family Enterobacteriaceae (Carson et al, 1999;Mey et al, 2002;Naka & Crosa, 2012;Stork et al, 2004;Wyckoff et al, 2007). However, to our knowledge, the ability of V. parahaemolyticus to utilize catecholate-type xenosiderophores has not yet been reported.…”

Complete Genome Sequence of the Marine Fish Pathogen Vibrio anguillarum Harboring the pJM1 Virulence Plasmid and Genomic Comparison with Other Virulent Strains of V. anguillarum and V. ordalii

“…The majority of the genes were conserved throughout the strains; however, the anguibactin biosynthesis and transport genes were found only on the pJM1 plasmid in the 775 strain, although the RV22 strain had homologues of the fatABCD genes. These genes appeared not to be expressed (5,51). The tonB1 and tonB2-ttpC clusters were found in all of the V. anguillarum strains, but only the tonB1 system was identified in V. ordalii.…”

Vibrio Iron Transport: Evolutionary Adaptation to Life in Multiple Environments

“…V. cholerae transports vibriobactin via the outer membrane receptor ViuA (94). Similarly, PvuA is the vibrioferrin receptor in V. parahaemolyticus (97), VuuA is the vulnibactin receptor in V. vulnificus (98), and FvtA transports vanchrobactin in V. anguillarum (99). The siderophore receptors are typically localized to the outer membrane without the need for accessory factors.…”