When a wine snob is going on about terroir, as wine snobs are wont to do, they're usually talking about the climate, terrain, and soil in which the grapes were grown. But in a paper just published in the journal mBio, researchers have taken terroir talk to a whole new and microscopic level: get ready to hear sommeliers talking about a wine's microbial life.
A team of researchers used resources at Argonne National Laboratory to compare the microorganisms living on and around Merlot plants from five vineyards on Long Island and from five plants from the Bordeaux region of France, as well as a few grapes from California. They found that, despite being separated by oceans and continents, samples from all three places had similar microbial communities.
"No matter where you are in the world, the types of bacteria growing on or in Merlot grapes are quite similar," Jack Gilbert, an Argonne Laboratory biologist and co-author on the study.
Microbes live all around and even in us, and we're just now starting to learn about and sequence their genomes. Wine grapes are a ripe subject to start studying; grapevines and their environs are already well studied. There's also an obvious economic incentive to hacking these microbial communities—if future research finds a microbe in one vineyard that makes the plants stand up better to disease or bad weather, it may be advantageous to introduce it elsewhere. If nothing else, there's almost definitely microbial communities that are impacting the wine's taste in some way.
The researchers found that there were different communities of bacteria living in the soil and on the roots compared to those living on the fruit, leaves and vines. The samples taken from above the ground varied more from plant to plant, as well as from the microbial communities living below the soil.
While no bacteria was found at all three sites on the plants, if they had common microbial ground, it was in the soil and roots. This led the researchers to conclude that the soil may be functioning as some sort of bacterial reservoir, and that descriptions of a terroir that are limited to just climate and soil type, but not microbial life, have been incomplete.
It may prove to be important, but it may take a while before sommeliers start mentioning that a wine is from a vineyard known for its robust Sphingomonas populations. Still, I'd advise you to at least start asking as soon as possible.