Four serotypes of Cryptococcus are responsible for most human and animal infections. C. gattii, serotype B and C, are the primary the causative agent of cryptococcosis in immune competent individuals whilst, C. neoformans var. neoformans serotype D, and C. neoformans var. grubii serotype A are most prevalent in immunocompromised hosts world-wide. C. gattii is recognized as a species distinct from C. neoformans based on differences in clinical manifestations, morphology, biological characteristics, and environmental niche. We used the plant model Arabidopsis thaliana plants and plant derived substrates as a model to explore C. gattii interactions in its ecological niche. C. gattii is distinguished from C. neoformans by the formation of distinct microtube structures during association with A. thaliana plants. Robust colonization of A. thaliana and microtube formation by C. gattii was found to require the transcriptional factor STE12α, the CAP59 gene essential for proper capsule structure but not the laccase 1 gene (LAC1) responsible for the synthesis of the laccase enzyme important for utilization of plant material and the production of melanin. The role of the transcriptional factor STE12 was consistent with known roles in the colonization of wood and reduced virulence in the mouse model system. Microtubes appeared as tube-like structures 0.04-0.1 μm in width and 0.5-3.0 μm in length, which terminate in a bulb-like structure. The central channel of the microtube appears continuous with cell cytoplasma and can contain vesicle-like bodies. C. gattii cells that formed microtubes as a result of association with plant matter were significantly more virulent in murine models of pulmonary and systematic cryptococcosis and more resistant to killing by human neutrophils in vitro. We suggest microtube formation is a structural adaptation for cell-cell and cell-host interaction. Such a distinct adaptation of C. gattii could play roles in its pronounced environmental association with trees and enhance virulence in mammalian hosts in comparison to C. neoformans. We propose C. gattii is a globally established pathogen with a specialized ecological niche on trees based on accumulation of reports on its wide spread temperate isolation from clinical, veterinary and environmental samples, array of dispersal mechanisms, and distinct formation of microtubes during association with plants or plant matter.
Some files may require a special program or browser plug-in. More Information
|Commitee:||Begley, Thomas, Chaturvedi, Sudha, Hanes, Steve, Melendez, Andre|
|School:||State University of New York at Albany|
|School Location:||United States -- New York|
|Source:||DAI-B 70/12, Dissertation Abstracts International|
|Subjects:||Molecular biology, Ecology, Microbiology|
|Keywords:||Cryprococcus gattii, Environmental niche, Geographic distribution, Laccase, Microtubes, Virulence|
Copyright in each Dissertation and Thesis is retained by the author. All Rights Reserved
The supplemental file or files you are about to download were provided to ProQuest by the author as part of a
dissertation or thesis. The supplemental files are provided "AS IS" without warranty. ProQuest is not responsible for the
content, format or impact on the supplemental file(s) on our system. in some cases, the file type may be unknown or
may be a .exe file. We recommend caution as you open such files.
Copyright of the original materials contained in the supplemental file is retained by the author and your access to the
supplemental files is subject to the ProQuest Terms and Conditions of use.
Depending on the size of the file(s) you are downloading, the system may take some time to download them. Please be