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Infection and Immunity, December 2006, p. 6949-6956, Vol. 74, No. 12
0019-9567/06/$08.00+0     doi:10.1128/IAI.00866-06
Copyright © 2006, American Society for Microbiology. All Rights Reserved.

Identification and Characterization of a Novel ABC Iron Transport System, fit, in Escherichia coli ^,

Zhiming Ouyang and Richard Isaacson^*

Department of Veterinary and Biomedical Sciences, University of Minnesota, 1971 Commonwealth Ave., St. Paul, Minnesota 55108

Received 31 May 2006/ Returned for modification 19 July 2006/ Accepted 6 September 2006

A putative ABC transporter, fit, with significant homology to several bacterial iron transporters was identified in Escherichia coli. The E. coli fit system consists of six genes designated fitA, -B, -C, -D, -E, and -R. Based on DNA sequence analysis, fit encodes an outer membrane protein (FitA), a periplasmic binding protein (FitE), two permease proteins (FitC and -D), an ATPase (FitB), and a hypothetical protein (FitR). Introduction of the E. coli fit system into E. coli strain K-12 increased intracellular iron content and transformed bacteria were more sensitive to streptonigrin, which suggested that fit transports iron in E. coli. Expression of fit was studied using a lacZ reporter assay. A functional, bidirectional promoter was identified in the intergenic region between genes fitA and fitB. The expression of the E. coli fit system was found to be induced by iron limitation and repressed when Fe²⁺ was added to minimal medium. Several fit mutants were created in E. coli using an in vitro transposon mutagenesis strategy. Mutations in fit did not affect bacterial growth in iron-restricted media. Using a growth promotion test, it was found that fit was not able to transport enterobactin, ferrichrome, transferrin, and lactoferrin in E. coli.

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* Corresponding author. Mailing address: Department of Veterinary and Biomedical Sciences, University of Minnesota, 1971 Commonwealth Ave., St. Paul, MN 55108. Phone: (612) 624-0701. Fax: (612) 625-5302. E-mail: isaac015{at}umn.edu.

Published ahead of print on 18 September 2006.

Editor: F. C. Fang

Supplemental material for this article may be found at http://iai.asm.org/.

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Infection and Immunity, December 2006, p. 6949-6956, Vol. 74, No. 12
0019-9567/06/$08.00+0     doi:10.1128/IAI.00866-06
Copyright © 2006, American Society for Microbiology. All Rights Reserved.

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