Identification of yeast and yeast-like fungal species in the Upper Midwest using physiological and DNA sequence data.

摘要

Yeasts are unicellular fungi that play key biological roles and are useful in many human applications from producing alcohol to serving as model organisms. They are found as free living organisms or as symbionts of animals and plants. An estimated 1% of the total extant species have been described. The objectives of this research focused on isolating and identifying yeast and yeast-like fungal species from the Upper Midwest using phenotypic tests and DNA sequencing. A total of 32 fungi showing single cell growth were isolated from plants, soil and compost from around the Upper Midwest. The isolates were purified and examined for morphological traits such as colony color, and cell characteristics. The isolates were tested physiologically in their abilities to utilize carbon and nitrogen compounds. A section of the large subunit rDNA was sequenced and compared to the same sequence from known species. Sequencing of the internal transcribed spacer regions of some of the isolates was also performed and compared to sequences from known species. A total of 14 species were identified with the most common species being Aureobasidium pullulans . Phylogenetic analyses showed the isolates as having diverse ancestry with isolates belonging to both the Ascomycetes and the Basidiomycetes. Two new species were found, one belonging to the genus Cryptococcus and another belonging to a new genus.