by Roberto
Several of our past posts described volatile organic compounds of microbial origin that influence our behavior. Acetates from wine, geosmin from soil. Not only are they enjoyable in the moment, such scents often elicit memories. I now offer the opposite perspective, a microbe whose ecology is influenced by a volatile organic compound of human origin. Baudoinia compniacensis, enter center stage.
The volatile accompanying our fungus in today's story is none other than ethanol. So simple, so powerful; particularly when distilled. Humans learned to ferment grains to produce alcoholic beverages more than 10,000 years ago. But it took several thousand more years to discover that boiling these beverages and condensing the vapors yielded much more potent concoctions. The art and science of alcohol distillation evolved slowly, but by the 12th century the process seems to have been widely used in China.
Fig. 1. Growth of the fungus Baudoinia compniacensis blackens a whisky distillery wall. Source
By the late 1800s distilleries were established worldwide. It was then that Anton Baudion, in whose honor today's main actor is named, recorded the description of a black sooty mold that grew abundantly near brandy distilleries in Cognac, France. Not that such sooty growth was unique to the region of Cognac. Identical microbial sightings were commonplace near distilleries everywhere. Turns out, B. compniacensis spores are widespread but the fungus does not outgrow its microbial neighbors unless there's ethanol in the air. It's been long known that some 2% of the ethanol in distilled spirits evaporates yearly during aging in barrels, this portion generally referred to as the Angel's Share. Not surprisingly, B. compniacensis is generally called the Angel's Share fungus: it has the striking ability to grow on ethanol vapors. What a nice story! Yeasts give fermented alcoholic beverages to humans who in turn seek more potent potions whose vapors are given back to the fungal world. But not everyone feels it's such a pleasant story. As you might expect, the bigger the distillery the more sooty black mold in their vicinity. Neighbors living next to large distilleries do not find it particularly pleasing that their trees, houses, and cars sport layer upon layer of Angel's Share fungal growth. And they are complaining! I can't really blame them. Just please don't blame B. compniacensis, blame human overconsumption. What else is new?
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