Wild yeast isolation by middle school students reveals features of North American oak populations of and .

Features of the natural life cycle of the budding yeast were crucial to its domestication as a laboratory experimental model, especially the ability to maintain stable haploid clones and cross them at will to combine alleles via meiosis. Stable haploidy results from mutations in , which encodes an endonuclease required for haploid-specific mating-type switching. Previous studies found an unexpected diversity of alleles among natural isolates within a small geographic area. We developed a hands-on field and laboratory activity for middle school students in Denver, Colorado, USA to isolate wild yeast from oak bark, identify species via DNA sequencing, and sequence from isolates. We find limited diversity in North American oak isolates, pointing to efficient, continuous dispersal across the continent. By contrast, we isolated the "dairy yeast", , from a tree <10 m away and found that it represents a new population distinct from an oak population in an adjacent state, pointing to high genetic diversity. The outreach activity partnered middle school, high school, and university students in making scientific discoveries and can be adapted to other locations and natural yeast habitats. Indeed, a pilot sampling activity in southeast Texas yielded oak isolates with a new allele of and, from a nearby prickly pear cactus, a heat-tolerant isolate of .