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ANNUAL CONFERENCE :: Abstract Library
Abstract Library
2003 Conference Abstract
| Type of Submission |
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Submission Type: |
Poster Presentation |
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Subject Category: |
Microbial Physiology |
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| Session Information |
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Presentation Date: |
May 27, 2003 |
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Abstract ID: |
E2 |
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Session: |
Poster 2 |
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Time: |
15:00 |
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| Presenting Author |
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| Other Authors |
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P.A. SOKOL, University of Calgary
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| Title |
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Characterization of a Burkholderia cepacia ABC Transporter System and its Potential Role in Iron Uptake |
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| Abstract Text |
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Pathogenic bacteria have at their disposition an arsenal of weapons that allow them to colonize and survive within different hosts and natural environments. Burkholderia cepacia has emerged as an important opportunistic pathogen in immunocompromised patients including those with cystic fibrosis, but can also commonly be found in soil, vegetation and water. Bacteria have evolved mechanisms to acquire iron from the host environment as a necessary virulence determinant. Competition for iron with mammalian iron-binding proteins can be achieved by mechanisms including siderophore production or direct acquisition via host proteins. Burkholderia cepacia has been reported to secrete four different siderophores and the siderophore ornibactin was shown to be an important virulence factor in a chronic respiratory infection model. In most Gram-negative bacteria, active transport of iron from the periplasm to the cytosol involves an ATP-binding cassette (ABC) transport system. One group of ABC transporters are the FbpABC homologues which include FbpA, a periplasmic iron-binding protein, FbpB, a cytoplasmic membrane permease, and FbpC, an inner membrane protein that interacts with FbpB to supply the energy to transport iron across the inner membrane by hydrolyzing ATP. An fbpABC locus was identified in B. cepacia. B. cepacia FbpA is 49, 46, and 36% identical to FbpA in Pasteurella multocida, Mannheimia haemolytica, and Pseudomonas aeruginosa, respectively. B. cepacia fbpABC complemented in trans an E. coli enterobactin negative strain (e573) and restored growth on medium with the iron chelator 2,2-dipyridyl, suggesting that these genes may be involved in iron uptake. No complementation of e573 was observed with only the fbpA gene indicating that the entire operon is required. FbpA homologues in other species are iron regulated. To evaluate the expression of fbpA under different iron concentrations, an fbpA transcriptional fusion was constructed using a promoter-less luxCDABEG broad-host-range vector. The results demonstrated that fbpA may not be iron regulated but growth regulated in B. cepacia. An fbpA knockout mutant was able to grow in iron-restricted conditions suggesting that these genes are not necessary for iron acquisition. Further studies will determine if the fbpABC genes are involved in siderophore-mediated iron uptake. |
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