Yeast is nothing shy of a magical form of life. Species of the single-celled fungal genus Saccharomyces feast on grape sugar and break it down to create alcohol molecules. By shearing carbon and oxygen atoms away from similar carbohydrates in decomposed barley, the yeast produces booze while shaking loose pockets of carbon dioxide that materialize as bubbles in a freshly cracked beer. And when the yeast produces those bubbles in dough, the result is bread’s delightfully airy texture.
Yeast turns grape sugar into alcohol / Flickr: ADD Photography
(Other genera of yeast fashion hard liquor, chocolate, soy sauce and scores of life’s other routine gastronomic indulgences out of 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 out of thin air?
The answer remains little known to scientists. But it rests in fungi’s remarkable ability to flood the environment with microscopic spores and to lay low, requiring little to no sustenance, until it settles on an abundant source of food that allows it to quickly flourish.
University of Florence and other European scientists on the hunt for Saccharomyces cerevisiae‘s winter hideouts reported yesterday in the Proceedings of the National Academy of Sciences [.pdf] a new discovery: It appears that this and other species of yeast thrive in the guts of social wasps that visit vineyards. Hibernating queens provide the yeast with a warm and safe winter home, and then the queens and their progeny help deposit the fungus back onto grapes as the fruit comes into season.
I suspect that this is just one of the many hiding places into which yeast can disappear when it’s not busily indulging in sugars and inadvertently serving our wont to inebriate. If the wasps disappeared, there probably would still be wine to be drunk. But the discovery highlights the adaptability of yeast, which helps to explain its fortuitous ubiquitousness in climates and vats around the world.
A video showing Saccharomyces cerevisiae, a strain of wine-producing yeast discovered in the guts of Italian wasps, under a microscope (the video was posted on YouTube by the MicrobiologyBytes Video Library):
[This yeast story was requested by reader Brent Bégin. Request your own here or on my Facebook page!]
