Wine-delivering wasps

By John Upton

Yeast is a salubrious if invisible vintner, and scientists have discovered an important role that wasps have played in its spread and evolution in vineyards around the world.

Species of the single-celled fungal genus Saccharomyces feast on grape sugar and break it down to create alcohol molecules.

(That’s not all, of course. By shearing carbon and oxygen atoms away from carbohydrates in decomposing barley, the yeast produces booze while shaking loose pockets of carbon dioxide that manifest as bubbles in a freshly cracked beer. When the yeast produces those bubbles inside dough, the result is bread’s delightfully airy texture. Other genera of yeast fashion hard liquor, chocolate, soy sauce and scores of life’s other routine gastronomic indulgences from otherwise questionably-edible ingredients.)

Most modern wine, beer and bread makers purchase Saccharomyces and pour the yeast directly into their concoctions. But wine, beer and bread emerged as staples long before anybody understood their microbiotic secrets — in various continents and countless cultures over at least the last 9,000 years. Many of these early vintners, brewers and bakers relied on nature to deposit the mystical ingredient into their potions.

Where did this yeast come from, if not from a packet? How could nature be so dependably relied upon to provide this ingredient, apparently from thin air?

Illustrated by Perry Shirley
Illustrated by Perry Shirley

The answer rests in fungi’s remarkable ability to flood the environment with its own microscopic spores and then to lay low, requiring little to no sustenance, until it settles on food that allows it to quickly flourish.

A team of French and Italian scientists reported in 2012 in Proceedings of the National Academy of Sciences that vineyard-visiting social wasps in Italy were found to be both vectors and natural reservoirs of S. cerevisiae. The group, which expects to publish follow-up research in the same journal shortly, concluded that the wasps served as a “key environmental niche for the evolution” of a yeast used for winemaking — a yeast that cannot spread through the air unaided.

The group found the yeast inside the guts and nests of wasps, suggesting that the insects inadvertently gather the yeast while foraging in vineyards for food. Hibernating queens provide the yeast with a warm and safe winter home, and then the progenies of the queens help deposit the fungus back onto grapes as the fruit comes into season.

“Our work suggests that wasps could move wine strains and maintain diversity, favoring crosses between strains involved in wine making and wild strains,” Duccio Cavalieri, a microbiology professor at the  University of Florence who was involved with the research.

(A version of this post originally appeared on Wonk on the Wildlife in 2012.)