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Iron Acquisition and Homeostasis in Histoplasma capsulatum

Hilty, Jeremy S.
http://rave.ohiolink.edu/etdc/view?acc_num=ucin1220026153

Abstract Details

2008, PhD, University of Cincinnati, Medicine : Cell and Molecular Biology.
Histoplasma capsulatum is a dimorphic fungal pathogen that survives and replicates within macrophages (MΦ). Studies in human and murine MΦ have demonstrated that the intracellular growth of H. capsulatum yeasts is exquisitely sensitive to the availability of iron. As H. capsulatum produces hydroxymate siderophores, we sought to determine if siderophore production was required for intracellular survival in MΦ, and in a murine model of pulmonary histoplasmosis. UC7 SIDA silenced yeasts and SIDA knockout yeasts (UC8 ΔsidA) grew normally in rich medium, did not synthesize siderophores, and were unable to grow on apotransferrin-chelated medium. The intracellular growth of UC7 SIDA silenced and UC8 ΔsidA yeasts in MΦ was significantly decreased compared to wild type (WT) yeasts, but growth was restored to WT levels by the addition of exogenous iron. Compared to WT (G217B) yeasts, C57BL/6 mice infected with demonstrated significantly reduced growth in the lungs and spleens seven days after infection. Additionally, we sought to identify specific genes required for intracellular survival, we utilized Agrobacterium tumefaciens-mediated mutagenesis, and screened for H. capsulatum insertional mutants that were unable to survive in human MΦ. One colony was identified that had an insertion within VMA1, the catalytic subunit A of the vacuolar ATPase (V-ATPase). The vma1 mutant (vma1::HPH) grew normally on iron replete medium, but not on iron deficient media. On iron deficient medium, the growth of the vma1 mutant was restored in the presence of wild type (WT) H. capsulatum yeasts, or the hydroxamate siderophore, rhodotorulic acid. However, the inability to replicate within MΦ was only partially restored by the addition of exogenous iron. The vma1::HPH mutant also did not grow as a mold at 28°C. The vma1::HPH mutant was avirulent in a mouse model of histoplasmosis. These studies demonstrate the importance of V-ATPase function in the pathogenicity of H. capsulatum, in iron homeostasis, and in fungal dimorphism and demonstrate that: SIDA expression is required for siderophore biosynthesis by H. capsulatum; that siderophore synthesis is required for optimum intracellular growth in MΦ and that in vivo, inhibition of siderophore synthesis reduces the virulence of H. capsulatum yeasts.
Simon Newman, PhD (Committee Chair)
George Smulian, MD (Committee Member)
Wallace Ip, PhD (Committee Member)
Steve Kleene, PhD (Committee Member)
Gary Dean, PhD (Committee Member)
111 p.
Biology
iron; histoplasma; vma; siderophore; fungal; siderophores; virulence

Recommended Citations

Citations

  • Hilty, J. S. (2008). Iron Acquisition and Homeostasis in Histoplasma capsulatum [Doctoral dissertation, University of Cincinnati]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1220026153

    APA Style (7th edition)

  • Hilty, Jeremy. Iron Acquisition and Homeostasis in Histoplasma capsulatum. 2008. University of Cincinnati, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=ucin1220026153.

    MLA Style (8th edition)

  • Hilty, Jeremy. "Iron Acquisition and Homeostasis in Histoplasma capsulatum." Doctoral dissertation, University of Cincinnati, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1220026153

    Chicago Manual of Style (17th edition)

ucin1220026153
422
© 2008, some rights reserved.Creative Commons License Iron Acquisition and Homeostasis in Histoplasma capsulatum by Jeremy S. Hilty is licensed under a Creative Commons Attribution-NonCommercial-NoDerivs 3.0 Unported License. Based on a work at etd.ohiolink.edu.
This open access ETD is published by University of Cincinnati and OhioLINK.