UC Riverside

Micro-colonial fungi (MCF) are an extremotolerant group of polyphyletic fungi found in different extremes of this planet, from Southern Californian deserts to Antarctic tundras, and even in the lungs of cystic fibrosis patients. MCF are found in the Eurotiomycetes and Dothideomycetes classes, two lineages that diverged millions of years ago, yet MCF from both these clades have developed nearly identical features. The work described in this thesis encompasses a wide range of MCF, uncovering their unusual niches, and understanding their genomic structure. The first chapter describes three new species of MCF isolated from biological soil crusts collected from the deserts of southern California. Two MCF, respectfully, use traditional Cahuilla tribal terms for nomenclature. We introduce to you Neophaeococcomyces mojaviensis, Coniosporium tulheliwenetii, and Taxawa tesnikishii. The second chapter has us travel to Antarctica where 25 strains of an endemic MCF, Friedmanniomyces endolithicus, were collected for 40 years and analyzed for geologic spatial placement, ploidy, and mating types. Within our population of 25, we received an interesting mix of ploidies and it may be the way F. endolithicus survives the extremes of Antarctica. We were also able to place the time of F. endolithicus divergence from other Dothideomycetes to 48 million years ago, near to the time predicted when Antarctica split from Pangea and drifted to the region it is found in today. Our final chapter takes us into the lungs of a cystic fibrosis patient to find a slow-growing MCF, Exophiala dermatitidis, persisting for over three years. Twenty-four specimens of E. dermatitidis were isolated from this patient in the span of three years with countless antibiotics to clear other persistent infections. Population structure showed three different groups with varying mutational rates, phenotypic filamentation, and chromosomal structures as possible main culprits for persistence. Heterogenous phenotypes were observed in the three groups, and we could not make ties to melanin pigmentation and itraconazole antifungal therapy. Through this work, it has become increasingly clear there needs to be more effort, whether in the clinical cases or environmental, to consider the slow-growing MCFs as possible causative agents or pivotal functional characters in different extreme habitats.