Microbial Terroir

Researchers show that microbes on the surface and stems of wine grapes are nonrandomly associated with the plant’s variety and geographic region.

Abby Olena
Abby Olena
Nov 26, 2013

FLICKR, SARAH ACKERMANMicrobes play a central role in turning grape must—mashed stems, seeds, skins, fruits, and juice—into wine. But now researchers from the University of California, Davis, have also shown that microbes specific to the cultivar or region of the wine grapes (Vitis vinifera) may contribute to terroir—the enigmatic, signature taste of a geographic area’s wine that has previously been attributed to water, soil, and climate. Their work was published yesterday (November 25) in Proceedings of the National Academy of Sciences.

“It’s likely that microbes play a larger role than presently known and are probably a part of the regional differences that we recognize,” Thomas Henick-Kling, a professor of oenology at Washington State University who was not involved in the study, told The New York Times.

The team used a short-amplicon sequencing approach on 273 grape must samples from multiple California locations and two different vintages—2010 and 2012. They showed that wine grapes in the same region or of the same variety carried a similar complement of bacteria and fungi, even though these microbial communities varied widely across the state. When they looked in depth at Chardonnay musts, the scientists found that both bacterial and fungal communities were highly specific to region. For Cabernet Sauvignon musts, however, only the fungal communities showed high regional specificity. The researchers determined that environmental conditions—especially rainfall and temperature highs and lows—were also correlated with the composition of grape must microbial communities, and that the bacterial and fungal complement of grape musts was fairly consistent in separate vintages.

“The reason I love this study is that it starts to walk down a path to something we could actually measure,” coauthor David Mills told The New York Times. “There are high-end courses on terroir, which I think are bunk. Someone has to prove that something about terroir makes it to the bottle, and no one has done that yet.”