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Infection and Immunity, June 2007, p. 2679-2688, Vol. 75, No. 6
0019-9567/07/$08.00+0     doi:10.1128/IAI.00076-06
Copyright © 2007, American Society for Microbiology. All Rights Reserved.

Quantitative Profile of the Uropathogenic Escherichia coli Outer Membrane Proteome during Growth in Human Urine

Department of Microbiology and Immunology, University of Michigan Medical School, 5641 West Medical Center Drive, Ann Arbor, Michigan 48109

Received 12 January 2007/ Returned for modification 26 February 2007/ Accepted 27 March 2007

Outer membrane proteins (OMPs) of microbial pathogens are critical components that mediate direct interactions between microbes and their surrounding environment. Consequently, the study of OMPs is integral to furthering the understanding of host-pathogen interactions and to identifying key targets for development of improved antimicrobial agents and vaccines. In this study, we used two-dimensional polyacrylamide gel electrophoresis (2D-PAGE) and tandem mass spectrometry to characterize the uropathogenic Escherichia coli (UPEC) outer membrane subproteome; 30 individual OMPs present on the bacterial surface during growth in human urine were identified. Fluorescence difference gel electrophoresis was used to identify quantitative changes in levels of UPEC strain CFT073 OMPs during growth in urine; six known receptors for iron compounds were induced in this environment, i.e., ChuA, IutA, FhuA, IroN, IreA, and Iha. A seventh putative iron compound receptor, encoded by CFT073 open reading frame (ORF) c2482, was also identified and found to be induced in urine. Further, the induction of these seven iron receptors in human urine and during defined iron limitation was verified by using quantitative real-time PCR (qPCR). An eighth iron receptor, fepA, displayed similar induction levels under these conditions as measured by qPCR but was not identified by 2D-PAGE. Addition of 10 µM FeCl₂ to human urine repressed the transcription of all eight iron receptor genes. A number of fecal-commensal, intestinal pathogenic, and uropathogenic E. coli strains all displayed similar growth rates in human urine, showing that the ability to grow in urine per se is not a urovirulence trait. Thus, human urine is an iron-limiting environment and UPEC enriches its outer membrane with iron receptors to contend with this iron limitation.

Published ahead of print on 9 April 2007.

Editor: A. D. O'Brien

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