Humans have been living with, cultivating, and using yeasts for millennia, long before we knew what they were. We’re still only beginning to understand how important they are in the natural world. Yeasts are everywhere: air, soil, orchards, vineyards, flower nectar, fruit. They live on our skin and in our digestive tracts.Saccharomyces cerevisiae, for example, is the sugar fungus that drives fermentation to give us bread, beer, and wine.Candida albicans, on the other hand, gives us yeast infections.

Only a fraction of the yeast species on the planet have been identified. We currently know of 1,500 species (of which Lachance has discovered 149; he has the genus Lachancea named after him), though Lachance pegs the potential total at 15,000. Other estimates have been ten times higher. Identifying a yeast strain used to take about eighty tests in a lab, but researchers are now able to go into landscapes with portable machines that can spit out genomic sequences to identify the sample. Meanwhile, hobbyists can go online to buy a Backyard Yeast Wrangling Tool Kit from Bootleg Biology and join the forefront of citizen science.

Yeasts have become a veritable “microbial workforce” in the biotech and health care industries, as Nicholas P. Money describes in his 2018 book The Rise of Yeast: How the Sugar Fungus Shaped Civilization. Yeasts have a cellular structure that is similar to humans’ and easy to manipulate. As a result, they are model organisms for research into genetics and cell biology. Yeasts are also used to make insulin, vaccines, leather, silk, riot-control spray, and ever-hopeful antiaging cosmetics. They are also touted as a potential key for future biofuels.

Wild yeasts have also become the darlings of the alcohol industry. Guelph-based Escarpment Labs, which launched in 2015, provides brewers with alternatives to commercial yeast strains. It now has a 1,100-strong collection, including a Nova Scotia sample dubbed “Driveway Carnage” and a variety that was mailed in by a yeast aficionado in Norway. Even Heineken recently released a “wild lager” made from a rare yeast discovered deep in Patagonia by microbiologist (and

Lachance collaborator) Diego Libkind.

The microbiome is having such a big moment that it’s hard to believe it’s been about 150 years since Louis Pasteur conducted experiments with grape juice to demonstrate that fermentation was the work of living microscopic entities. New breakthroughs are still happening regularly and can challenge our perceptions of the natural world.

Lachance recounts discovering a yeast species endemic to the Great Lakes region in a patch of morning glories near his campus. Lachance assumed that the Metschnikowia borealis, which has cousins from Florida to Costa Rica to Hawaii, grew in the flowers, but he later came to suspect that it lived in the gut of the nitidulid beetles that feed and breed in the trumpet-shaped blooms. When captured insects wandered over agar plates, they left behind looping trails that soon became yeast colonies. A colleague suggested that Lachance use Krazy Glue to prevent the beetles from excreting, and the evidence was right there on the plate—or, rather, it wasn’t. It appears the bugs aren’t just carrying the yeast inside them—they’re actually growing it on the flowers, likely for nutritional benefit. Although, the more we learn more about yeasts, the harder it becomes to tell whether we’re cultivating them or they’re cultivating us.