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Wine experts use the term terroir to describe the physical properties of a vineyard—the climate, the type of soil, the agricultural history of the land—that contribute to the unique characteristics of its wines. Terroir is the reason a Merlot from one vineyard may taste different from one made at a different vineyard just a few miles away, and those differences apparently have as much to do with the bacteria living in the soil as the more obvious physical characteristics of the land.

In a new study published in the journal mBio, University of Chicago microbiologist Jack Gilbert, PhD, and his team analyzed the bacteria living in and around similar Merlot grapevines from vineyards in Long Island, New York. They found that the majority of bacteria in the grapes originated from the soil, and the microbiome, or bacterial community, of the plant differs depending on the microbiome of the surrounding soil, even among the same stock of vines grown just a few miles apart.

While these differences contribute to terroir and the ultimate taste of wines, a vine’s microbiome also contributes to its disease resistance, stress tolerance and productivity, all major agricultural concerns as the climate changes.

“Different areas of the plant have different microbiomes, but in nearly all cases, the microbiome originates with the soil,” Gilbert said. “Everyone latches onto terroir because that’s the most interesting thing about vines, but there’s a much larger story here with regards to the role the soil plays in the development of the productivity, disease tolerance and stress tolerance of the plant itself.”

Gilbert and his team from UChicago and Argonne National Laboratory worked with Gilles Martin, head winemaker at Sparkling Pointe winery in Long Island, to collect samples of Merlot vines, leaves, roots and the soil around them every season for two years. Samples were taken from five different vineyards within a five-mile radius, all farmed by the same winery.

The Merlot vines from each vineyard areas shared common bacterial species, but plants from each site had slight differences in their microbiome driven by differences in the soil. This suggests that the soil is an important reservoir for bacteria, and site-by-site differences influence the microbes in the plants.

“The types of bacteria that influence different physiological processes in the plant are going to affect the chemistry of the grape, and that might be the elusive component that links soil conditions to terroir,” Gilbert said. “When you’re a winemaker and you’re blending grapes from different vineyards in your region to create your perfect wine, then those very subtle influences have a big impact.”

Those bacteria also influence the plants’ ultimate health and productivity, including their ability to withstand higher temperatures and changing moisture levels accompanying ongoing changes in climate. Gilbert said that some day winemakers may be able to manipulate the bacterial makeup of vineyards to produce hardier plants, or preserve that all important terroir as environmental conditions change.

Wine is big business after all, and the industry’s survival may depend on a deeper appreciation of the microbiome’s influence.

“Viticulturists need some help. Climate change is coming, and they’re going to be in a situation where their crops are under stress,” Gilbert said. “We’re keen to make sure U.S. viticulturists have the most advanced tools at their hands to make sure they adapt to the changing environment to create the best wines possible and be competitive on the global market.”

All images by Jack Gilbert and Kristen West/FMC Corporation

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