Yeast is a well-known component for bakers and vintners, yet recent studies from the University of Georgia indicate it may also follow the paths of our forebears.

Humans began to cultivate baker’s yeast as early as 7000 BCE for producing bread, beer, wine, and sake. However, wild strains of the same yeast species also inhabit trees. These cultivated and wild yeasts display different genetic characteristics, but UGA researchers were eager to investigate potential connections between them.

“Other research had begun to indicate that baker’s yeast found in forests differs, and some of my previous observations in Europe suggested that the forest strains were distinct from the cultivated strains,” stated Douda Bensasson, the lead author of the study and an associate professor in UGA’s Franklin College of Arts and Sciences Department of Plant Biology.

“However, we aimed to delve deeper and classify the varied groups in both America and Europe.”

The research utilized publicly accessible data globally and samples from tree bark in various locales, primarily the southeastern U.S. (Some samples were gathered on UGA’s North Campus close to the Arch.)

The scientists extracted and examined DNA from the yeast they collected. They subsequently used this information to compare genetic compositions across different regions.

“We are observing clear subpopulations within continents,” remarked Jacqueline Peña, the primary author of the study and a Ph.D. candidate in UGA’s Department of Plant Biology. “We’re discovering that, even though we initially assumed these wild populations would differ significantly, they don’t seem entirely disconnected from human influence.”

It remains uncertain how microorganisms such as yeast thrive in their natural environments. Consequently, the researchers cautioned that humans could be effecting significant changes to the ecosystem without recognizing it.

Migrations during the last ice age might have influenced yeast distribution

To gather yeast samples, researchers peeled off sections of tree bark and stored them in sealed tubes. Using a method similar to winemaking to encourage yeast growth, the scientists examined its DNA to ascertain when different groups diverged.

“We anticipated that these would show early separations, and that the yeast from forests would have no association with humans whatsoever,” Bensasson explained. “To our astonishment, we discovered that it roughly aligned with the last ice age, which coincides with the period when humans began cultivating their food and disseminating agriculture worldwide.”

Peña described this scenario as a “unique duality,” indicating both wild and cultivated varieties of yeast exist, but both have been shaped in some manner by human actions.

Yeast from the southern U.S. identified in southern Europe

While studying yeast samples from various regions, Peña and Bensasson stumbled upon something unusual — the yeast found in the winemaking areas of southern Europe bore resemblance to those from the southern U.S. Their findings indicated the yeast had been imported from the U.S. in recent centuries.

The researchers suspect this could be attributed to the Great French Wine Blight. In the 1850s, an insect pest was unintentionally introduced to Europe, causing widespread destruction to vineyards.

In an effort to salvage the wine industry, laborers transported pest-resistant vines from North America. As they couldn’t produce wine from the lower quality grapes, they instead grafted European vines onto the North American rootstocks. In doing so, yeasts residing within the North American vines were transferred to their European counterparts.

Humans might have a more significant effect on wild yeast today

Investigating yeast in this fashion provides a unique perspective on how humans have navigated and interacted with their surroundings. However, Bensasson expressed concerns about the modifications we may be enacting on our environment.

“If humans, unintentionally, were dispersing microbes thousands of years ago, just consider all the actions we are undertaking now,” Bensasson remarked. “We could be altering numerous elements without our awareness. I can’t determine if that’s positive or negative, but it’s somewhat alarming that we lack clarity on our impact.”

The research was published in Molecular Ecology and co-written by Eduardo Scopel and Audrey Ward.

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