POPULATION GENETICS AND GENOMICS OF COCCIDIOIDES IMMITIS AND COCCIDIOIDES POSADASII

Persistent Link:
http://hdl.handle.net/10150/193909
Title:
POPULATION GENETICS AND GENOMICS OF COCCIDIOIDES IMMITIS AND COCCIDIOIDES POSADASII
Author:
Barker, Bridget M.
Issue Date:
2009
Publisher:
The University of Arizona.
Rights:
Copyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.
Abstract:
The goal of my dissertation research is to elucidate the population structure of two understudied but increasingly important fungal pathogens of humans. Coccidioides immitis and C. posadasii cause the disease coccidioidomycosis (Valley fever). These fungi occur in the soil of the desert regions of North and South America. Although studied for over 100 years, the primary host, ecological niche, and sexual cycle of Coccidioides spp. still remain unknown. Understanding the population structure of these fungi will permit identification of fundamental aspects of their ecology and allow researchers to identify potential hosts. Assessing genotypic diversity of pathogens is one step to understanding the population structure and evolutionary potential of organisms, and is the focus of this dissertation. The first appendix focuses on developing and evaluating methods to obtain environmental samples, and comparison of genotypes found in soil vs. human patients. Direct inoculation of mice proved to be the most reliable method of obtaining environmental strains. Environmental isolates from Tucson group with Arizona patient isolates. Comparing genotypes of human, environmental and non-human host strains of Coccidioides may help to determine if gene flow occurs over long distances and provide some indication of the population structure of C. posadasii in the environment, and is the focus of the second appendix. Finally, whole-genome sequencing and resequencing has been completed for 20 strains of C. immitis and C. posadasii. The resulting data provide greater insight into variation between and within species. In particular, the final appendix provides evidence for hybridization and gene flow between species. Data show that a region of C. posadasii origin is found at a higher frequency among the C. immitis southern California and Mexico patient isolates, and is found rarely among patient isolates from the San Joaquin Valley. Of particular interest is the fact that there is a conserved border region for all instances of introgression, and the gene immediately adjacent to this border is a metalloproteinase gene. Together these studies provide insight into the population biology of two human pathogenic fungi: gene flow is limited between species and populations, but genetic exchange occurs at all levels.
Type:
text; Electronic Dissertation
Keywords:
Fungal pathogenesis; Hybridization; Introgression; Mycology; Soil
Degree Name:
Ph.D.
Degree Level:
doctoral
Degree Program:
Genetics; Graduate College
Degree Grantor:
University of Arizona
Advisor:
Rounsley, Steve
Committee Chair:
Rounsley, Steve

Full metadata record

DC FieldValue Language
dc.language.isoenen_US
dc.titlePOPULATION GENETICS AND GENOMICS OF COCCIDIOIDES IMMITIS AND COCCIDIOIDES POSADASIIen_US
dc.creatorBarker, Bridget M.en_US
dc.contributor.authorBarker, Bridget M.en_US
dc.date.issued2009en_US
dc.publisherThe University of Arizona.en_US
dc.rightsCopyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.en_US
dc.description.abstractThe goal of my dissertation research is to elucidate the population structure of two understudied but increasingly important fungal pathogens of humans. Coccidioides immitis and C. posadasii cause the disease coccidioidomycosis (Valley fever). These fungi occur in the soil of the desert regions of North and South America. Although studied for over 100 years, the primary host, ecological niche, and sexual cycle of Coccidioides spp. still remain unknown. Understanding the population structure of these fungi will permit identification of fundamental aspects of their ecology and allow researchers to identify potential hosts. Assessing genotypic diversity of pathogens is one step to understanding the population structure and evolutionary potential of organisms, and is the focus of this dissertation. The first appendix focuses on developing and evaluating methods to obtain environmental samples, and comparison of genotypes found in soil vs. human patients. Direct inoculation of mice proved to be the most reliable method of obtaining environmental strains. Environmental isolates from Tucson group with Arizona patient isolates. Comparing genotypes of human, environmental and non-human host strains of Coccidioides may help to determine if gene flow occurs over long distances and provide some indication of the population structure of C. posadasii in the environment, and is the focus of the second appendix. Finally, whole-genome sequencing and resequencing has been completed for 20 strains of C. immitis and C. posadasii. The resulting data provide greater insight into variation between and within species. In particular, the final appendix provides evidence for hybridization and gene flow between species. Data show that a region of C. posadasii origin is found at a higher frequency among the C. immitis southern California and Mexico patient isolates, and is found rarely among patient isolates from the San Joaquin Valley. Of particular interest is the fact that there is a conserved border region for all instances of introgression, and the gene immediately adjacent to this border is a metalloproteinase gene. Together these studies provide insight into the population biology of two human pathogenic fungi: gene flow is limited between species and populations, but genetic exchange occurs at all levels.en_US
dc.typetexten_US
dc.typeElectronic Dissertationen_US
dc.subjectFungal pathogenesisen_US
dc.subjectHybridizationen_US
dc.subjectIntrogressionen_US
dc.subjectMycologyen_US
dc.subjectSoilen_US
thesis.degree.namePh.D.en_US
thesis.degree.leveldoctoralen_US
thesis.degree.disciplineGeneticsen_US
thesis.degree.disciplineGraduate Collegeen_US
thesis.degree.grantorUniversity of Arizonaen_US
dc.contributor.advisorRounsley, Steveen_US
dc.contributor.chairRounsley, Steveen_US
dc.contributor.committeememberVan Etten, Hansen_US
dc.contributor.committeememberOrbach, Marcen_US
dc.contributor.committeememberArnold, Anne Elizabethen_US
dc.identifier.proquest10702en_US
dc.identifier.oclc659753479en_US
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