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Journal of Bacteriology, September 2006, p. 6515-6523, Vol. 188, No. 18
0021-9193/06/$08.00+0     doi:10.1128/JB.00626-06
Copyright © 2006, American Society for Microbiology. All Rights Reserved.

Characterization of Ferric and Ferrous Iron Transport Systems in Vibrio cholerae

Elizabeth E. Wyckoff,* Alexandra R. Mey, Andreas Leimbach,{dagger} Carolyn F. Fisher, and Shelley M. Payne

Section of Molecular Genetics and Microbiology and Institute of Cellular and Molecular Biology, The University of Texas, Austin, Texas 78712

Received 2 May 2006/ Accepted 11 July 2006

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 the V. cholerae genome sequence. Clones encoding either the Feo or the Fbp system exhibited characteristics of iron transporters: both repressed the expression of lacZ cloned under the control of a Fur-regulated promoter in Escherichia coli and also conferred growth on a Shigella 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 the S. 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 of V. 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.


* Corresponding author. Mailing address: The University of Texas, Section of Molecular Genetics and Microbiology, 1 University Station A5000, Austin, TX 78712-0162. Phone: (512) 471-5204. Fax: (512) 471-7088. E-mail: ewyckoff{at}mail.utexas.edu.

{dagger} Present address: Am Hubland 16B, Apt. 2408, 97074 Wurzburg, Germany.


Journal of Bacteriology, September 2006, p. 6515-6523, Vol. 188, No. 18
0021-9193/06/$08.00+0     doi:10.1128/JB.00626-06
Copyright © 2006, American Society for Microbiology. All Rights Reserved.




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