Open AccessCharacterization of Ferric and Ferrous Iron Transport Systems in Vibrio cholerae
Author(s) -
Elizabeth E. Wyckoff,
Alexandra R. Mey,
Andreas Leimbach,
Carolyn Fisher,
Shelley M. Payne
Publication year - 2006
Publication title -
journal of bacteriology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.652
H-Index - 246
eISSN - 1067-8832
pISSN - 0021-9193
DOI - 10.1128/jb.00626-06
Subject(s) - vibrio cholerae , siderophore , biology , atp binding cassette transporter , mutant , ferrous , periplasmic space , ferrichrome , ferroportin , biochemistry , permease , bacterial outer membrane , escherichia coli , membrane transport protein , transporter , enterobactin , operon , ferric , transport protein , gene , chemistry , bacteria , genetics , organic chemistry , iron homeostasis
Vibrio cholerae has multiple iron acquisition systems, including TonB-dependent transport of heme and of the catechol siderophore vibriobactin. Strains defective in both of these systems grow well in laboratory media and in the infant mouse intestine, indicating the presence of additional iron acquisition systems. Previously uncharacterized potential iron transport systems, including a homologue of the ferrous transporter Feo and a periplasmic binding protein-dependent ATP binding cassette (ABC) transport system, termed Fbp, were identified in theV. cholerae genome sequence. Clones encoding either the Feo or the Fbp system exhibited characteristics of iron transporters: both repressed the expression oflacZ cloned under the control of a Fur-regulated promoter inEscherichia coli and also conferred growth on aShigella flexneri mutant that has a severe defect in iron transport. Two other ABC transporters were also evaluated but were negative by these assays. Transport of radioactive iron by the Feo system into theS. flexneri iron transport mutant was stimulated by the reducing agent ascorbate, consistent with Feo functioning as a ferrous transporter. Conversely, ascorbate inhibited transport by the Fbp system, suggesting that it transports ferric iron. The growth ofV. cholerae strains carrying mutations in one or more of the potential iron transport genes indicated that both Feo and Fbp contribute to iron acquisition. However, a mutant defective in the vibriobactin, Fbp, and Feo systems was not attenuated in a suckling mouse model, suggesting that at least one other iron transport system can be used in vivo.