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Infection and Immunity, November 2006, p. 6171-6178, Vol. 74, No. 11
0019-9567/06/$08.00+0 doi:10.1128/IAI.00874-06
Copyright © 2006, American Society for Microbiology. All Rights Reserved.
Department of Microbiology, Immunology, and Molecular Genetics, University of Kentucky, Lexington, Kentucky
Received 1 June 2006/ Returned for modification 28 June 2006/ Accepted 16 August 2006
In addition to the yersiniabactin (Ybt) siderophore-dependent system, two inorganic iron ABC transport systems of Yersinia pestis, Yfe and Yfu, have been characterized. Here we show that the Yfu system functions in Y. pestis: a Ybt Yfe Yfu mutant exhibited a greater growth defect under iron-deficient conditions than its Ybt Yfe parental strain. We also demonstrate that another putative Y. pestis iron uptake system, Yiu, which potentially encodes an outer membrane receptor, YiuR, and an ABC iron transport cassette, YiuABC, is functional. The cloned yiuABC operon restored growth of an enterobactin-deficient mutant Escherichia coli strain, 1017, under iron-chelated conditions. Iron uptake by the Yiu system in Y. pestis was demonstrated only when the Ybt, Yfe, and Yfu systems were mutated. Using a yiuA::lacZ fusion, we show that the yiuABC promoter is repressed by iron through Fur. A mouse model of bubonic plague failed to show a significant role for the Yiu system in the disease process. These results demonstrate that two additional iron transporters are functional in Y. pestis and indicate that there is a hierarchy of iron transporters, with Ybt being most effective and Yiu being the least effective of those systems which have been characterized.
Published ahead of print on 5 September 2006.
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