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Functional complementation of ΔexbD E. coli by homologous exbD genes

Abstract Details

2013, Master of Science (MS), Bowling Green State University, Biological Sciences.
The TonB system energizes the high affinity transport of ferric siderophores in gram negative bacteria. Within this system, there are three main proteins: TonB, ExbB, and ExbD. This study was focused on the role of the ExbD protein in the system. The hypothesis that ExbD is responsible for recycling TonB was examined by a strategy in which homologous exbD genes were used to complement an E. coli exbD strain. The more closely related species' exbD gene conferred functionality better than exbD genes from more distantly related species. The exbD homologues from Serratia liquefaciens, Yersinia entercolitica, Proteus mirabilis, and Vibrio parahaemolyticus were tested. The ability of ExbD homologues to support TonB function was evaluated by performing sensitivity assays against colicins and bacteriophage in E. coli with the exbD gene from each of the different species. I found that exbD genes from all species except for the Vibrio rendered E. coli sensitive to these agents. A more precise iron transport assay was performed and it showed similar results to the killing assays. ExbD from Serratia, Proteus, and Yersinia, were each able to to support the TonB-dependent transport of ferric siderophore across the outer membrane, albeit less with less efficiency in the case of Yersinia. As with the killing assays, here the Vibrio exbD genes were again unable to support a TonB-dependent process. However, studies of TonB half life indicated that, while unable to support TonB activity, the ExbDs from Vibrio still conferred stability to TonB in E. coli, suggesting that they did assemble into the proton translocating complex and did associate with TonB. This suggests that ExbD may play a role in proper positioning of TonB. These results indicate that ExbD plays a more active role within the TonB system than originally contemplated.
Ray A. Larsen (Advisor)
Vipa Phuntumart (Committee Member)
Paul Morris (Committee Member)

Recommended Citations

Citations

  • Butler, K. A. (2013). Functional complementation of ΔexbD E. coli by homologous exbD genes [Master's thesis, Bowling Green State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=bgsu1377012630

    APA Style (7th edition)

  • Butler, Kate. Functional complementation of ΔexbD E. coli by homologous exbD genes. 2013. Bowling Green State University, Master's thesis. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=bgsu1377012630.

    MLA Style (8th edition)

  • Butler, Kate. "Functional complementation of ΔexbD E. coli by homologous exbD genes." Master's thesis, Bowling Green State University, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=bgsu1377012630

    Chicago Manual of Style (17th edition)