A walk on the wild side

On a break from teaching microbiology to University of Minnesota students, Dana Davis noticed a coyote out in the open.

Coyotes are common enough near the College of Biological Sciences’ field station in northern Minnesota. But when this one interrupted its trot across the station’s soccer field to leave a steaming pile of scat (feces), Davis saw a gold mine of material for finishing the day’s lesson.

He quickly scooped up the deposit, hurried back to his lab, and plated a diluted sample out on a petri dish containing a solid, agar-based support on which yeast colonies would grow. These served as models of what cultured yeast colonies look like. They also became part of Davis’s five-year history of collecting wildlife scat at University field sites like Cedar Creek Ecosystem Science Reserve and the Itasca Biological Station and Laboratories.

The numerous yeast colonies led to some astonishing discoveries.

For example, Davis found that wildlife commonly carry Candida albicans (C. albicans), a yeast that causes human conditions like thrush, diaper rash, and candidiasis. And his discoveries don’t stop there.

“What was more interesting was that the vast majority of things that [we] identified or cultured had never been characterized or identified before,” says Davis. “There were brand new species.” 

About 12 of them, he figures.

Soon Davis was teaching students at both University field sites to collect scat from various wild animals, then grow, study, and identify yeast colonies from each sample. From a student interest angle, yeast was a good choice because it comes in a variety of colors and growth patterns. Trained students now collect samples on their own, at the field stations and elsewhere.

A boost from beer

An admitted beer aficionado, Davis began his Ph.D. work studying Saccharomyces cerevisiae, or “brewer’s yeast.”

“Most things in my life revolve around or are facilitated by beer,” he admits.

Davis now studies how yeasts, especially C. albicans, respond to environmental change. But he wants to know more about the conditions in which the yeast could survive and thrive, which could have medical implications.

His work raises lots of questions: Why can certain immune systems respond to specific yeasts better than others? Can yeasts thrive in multiple hosts and jump, say, from dog to owner or from deer to mouse? And how do they mutate along the way?

“Students were so excited about collecting scat samples and grinding them up and plating,” he says. “They were definitely into it. I just decided—why not loop students into something that’s contributing to real research as well?”

This story is adapted from an article by the College of Biological Sciences.