(VinePair) - Here’s one science lesson worth the flop sweat and trembling limbs we used to get when we were asked to balance an equation or memorize terms like Avogadro’s Number and phalanges. Why is this particular lesson worthwhile? ‘Cause it’s about beer.

Before panic sets in, let’s just clarify the scary-seeming term: Brettanomyces is a kind of yeast (Brettanomyces literally means “British fungus,” but not because the Brits invented it; the stuff was discovered when a scientist was looking into spoilage of some English ales). A “wild” yeast (we’ll get to that) that can have a desirable, or less desirable, impact on the fermentation, and therefore flavor, of beer. It’s a good time to learn about brettanomyces, or “brett” as it’s known in the industry, and not just for basic drinker’s upsmanship; the stuff is showing up increasingly on the craft beer shelf.

Before we get into brett, a quick primer on yeast and fermentation: yeast eat sugar and create alcohol and carbon dioxide. There are various species of yeast, but the one most commonly associated with the production of beer is a strain called Saccharomyces cerevisiae. (Think “cerveza” and “cerevisiae,” it’s a good way to remember.) Among many other factors (hop and malt varieties, water/mineral content, fermentation temperature, etc.), the kind of yeast used in fermentation will impact the final flavor of the beer. That’s why some craft brewers cultivate specific strains of yeast and guard them like trolls under a bridge.

ut Brettanomyces (actually a genus) is a bit of a yeast maverick. So-called “wild” yeast, it’s been the scourge, and then the friend, of brewers for centuries. See, Brettanomyces grow naturally on fruit skins, which means in a brewery environment, which historically might have been very much in proximity to a farm or produce, there’s brett aplenty. Which is why back in the day, before sanitation methods were as extensive, brewers often ended up with a partially brett-fermented beer. The stuff existed in the ambient environment, and, yeast being the greedy bastard that it is, found its way into the tank of glucose-rich fermenting grains.

Why would a brewer want to protect his beer from brett? Because, unlike S. cerevisiae, the flavors you might get from a Brett-fermented beer are particularly distinctive, with an emphasis on funkiness, spice, fruit, and a bit of tartness (Brett specifically produces acetic acid).