CENTENNIAL HONORS COLLEGE
Western Illinois University
Undergraduate Research Day 2015
Podium Presentation
Diversity and Distribution Analysis of Yeasts in an Arid Grassland Ecosystem in Utah
Aleshia Johannsen
Faculty Mentor: Andrea Porras-Alfaro
Biology
Yeasts are essential components to environmental and human microbial communities and are responsible
for many opportunistic fungal infections, yet little is known about their diversity, ecological roles, and
distribution in natural ecosystems. The objective of this study is to culture and identify yeasts present in
rhizosphere soil and biological soil crust in an arid grassland ecosystem in Utah. The soil samples were
diluted and plated on selective media and incubated at 35°C and 25°C. Pure cultures were isolated on
PYG and MEA with antibiotics. Most yeast cultures were most successfully isolated on MEA media at
25°C. A total of 37 yeasts were isolated and identified using molecular methods. Morphological diversity
was high with nine dominant morphotypes. Yeasts were obtained from all soil types suggesting a wide
distribution in the different microenvironments. Most isolates were from August 2013 (57%) and the least
from February and March 2014 (3%). A higher number of yeasts were isolated from below-lichen soil
crust (22%) and the least from moss crust (3%). Yeast cultures were sequenced for identification using
ITS, LSU, and SSU rDNA fungal primers. The analysis of multiple genes is necessary to determine
taxonomic classification of yeasts. Sequences were compared with databases in GenBank, NCBI
nucleotide blast, and curated fungal databases such as UNITE. The most common phylum was
Basidiomycota. Lecythophora/Coniochaeta complex and Cryptococcus spp. were the most abundant
genera in addition to other yeasts such as Bulleromyces, Tilletiopsis washingtonensis, and Rhodotorula
mucilaginosa. Phylogenetic analyses are being conducted to determined taxonomic placement of the yeast
isolates.