Genetics and environmental regulation of Shigella iron transport systems |
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Authors: | Elizabeth E Wyckoff Megan L Boulette Shelley M Payne |
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Institution: | (1) Section of Molecular Genetics and Microbiology, Institute for Cellular and Molecular Biology, University of Texas, Austin, TX 78712, USA |
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Abstract: | Shigella spp. have transport systems for both ferric and ferrous iron. The iron can be taken up as free iron or complexed to a variety
of carriers. All Shigella species have both the Feo and Sit systems for acquisition of ferrous iron, and all have at least one siderophore-mediated
system for transport of ferric iron. Several of the transport systems, including Sit, Iuc/IutA (aerobactin synthesis and transport),
Fec (ferric di-citrate uptake), and Shu (heme transport) are encoded within pathogenicity islands. The presence and the genomic
locations of these islands vary considerably among the Shigella species, and even between isolates of the same species. The expression of the iron transport systems is influenced by the
concentration of iron and by environmental conditions including the level of oxygen. ArcA and FNR regulate iron transport
gene expression as a function of oxygen tension, with the sit and iuc promoters being highly expressed in aerobic conditions, while the feo ferrous iron transporter promoter is most active under anaerobic conditions. The effects of oxygen are also seen in infection
of cultured cells by Shigella flexneri; the Sit and Iuc systems support plaque formation under aerobic conditions, whereas Feo allows plaque formation anaerobically. |
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Keywords: | Iron transport Pathogenicity islands Shigella Feo Aerobactin Sit |
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