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CELL SHAPE DETERMINATION IN ESCHERICHIA COLI

Bendezu, Felipe Oseas
http://rave.ohiolink.edu/etdc/view?acc_num=case1215459479

Abstract Details

2008, Doctor of Philosophy, Case Western Reserve University, Molecular Biology and Microbiology.
The load-bearing exoskeleton, known as the murein sacculus, is believed to impart the shape of bacterial cells. The chemical composition and enzymes responsible for building this bag-like structure are fairly well understood. What is lacking, however, is a detailed understanding of how the bacterial cell coordinates the spatio-temporal synthesis of the sacculus to achieve a complex shape. It is now clear that many genera of bacteria use the cytoskeletal actin protein MreB to accomplish this. However, the precise mechanism by which MreB actin contributes to complex cell shape determination is not known. A popular model states that MreB spiral-like cyto-filaments serve as a track to direct the placement of new murein material. In the well-studied bacterium Escherichia coli, MreB is one of five known proteins needed for rod-shape growth, with the others being MreC, MreD, PBP2 and RodA. How loss of one or more of these proteins affects cell physiology has been a confusing issue. In attempts to bring clarity into this field of research, I created a defined and comprehensive set of shape mutants and analyzed their phenotypes. These studies showed that all five are only conditionally essential. Cells lacking one or more of these proteins were able to survive when grown under conditions of slow mass increase or when the essential division protein FtsZ is over-expressed. Intriguingly, when grown under conditions of fast mass increase, mutant cells grow into giant spheres that are unable to regulate important cellular processes and eventually die. These spheres accumulate excess membrane in their interior that compete with the cell membrane for essential division proteins and I propose that this contributes significantly to the lethal division defect under non-permissive conditions. I used the fact that extra FtsZ can rescue life to shape-defective mutants as the basis for a genetic screen to identify additional shape mutants. This identified an uncharacterized membrane protein we named RodZ. Cells lacking RodZ display an impressive set of media and temperature-influenced shape defects. Also, using the first fully function fluorescent fusion protein to MreB, I was able to show that RodZ is essential for proper MreB assembly.
Piet de Boer (Advisor)
Erik Andrulis (Committee Chair)
Patrick Viollier (Committee Member)
Pieter de Haseth (Committee Member)
Arne Rietsch (Committee Member)
238 p.
Cellular Biology; Genetics; Microbiology; Molecular Biology
bacterial cell shape; MreB; bacterial actin

Recommended Citations

Citations

  • Bendezu, F. O. (2008). CELL SHAPE DETERMINATION IN ESCHERICHIA COLI [Doctoral dissertation, Case Western Reserve University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=case1215459479

    APA Style (7th edition)

  • Bendezu, Felipe. CELL SHAPE DETERMINATION IN ESCHERICHIA COLI. 2008. Case Western Reserve University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=case1215459479.

    MLA Style (8th edition)

  • Bendezu, Felipe. "CELL SHAPE DETERMINATION IN ESCHERICHIA COLI." Doctoral dissertation, Case Western Reserve University, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=case1215459479

    Chicago Manual of Style (17th edition)

case1215459479
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© 2008, all rights reserved.
This open access ETD is published by Case Western Reserve University School of Graduate Studies and OhioLINK.