Five hundred years ago, when Europeans explorers began crossing the Atlantic, a particular strain of wild yeast traveled back to Europe with them. It merged with the yeasts that were used for making ales in the Bavarian region of what is now Germany, producing a hybrid strain that allowed for slower, colder fermentation. People have been enjoying lager-style beers ever since, including Coors and Budweiser. But until now, nobody knew where that mysterious yeast came from.
Writing this week in the Proceedings of the National Academy of Sciences, an international team has announced the discovery of a wild yeast species, dubbed Saccharomyces eubayanus, that appears to be the long-lost parent strain of lager yeast. It was discovered in the beech forests of Patagonia, at the southern tip of South America. Beech trees provide a sugary environment, which would have made this species well-adapted for the fermentation process of beer—in which sugars from grains are converted to alcohol.
Gene sequencing, performed at the University of Colorado School of Medicine, showed the Patagonian yeast was distinct from all other known wild yeasts. But its DNA was 99.5 percent identical to the non-ale portions of the lager yeast genome.
So the next time you’re enjoying a cold lager, think of the yeast that travelled 7,000 miles from Patagonia to Bavaria and raise a toast to Saccharomyces eubayanus—hopefully it gets easier to pronounce with each glass of beer.
A version of this story was featured on the August 23, 2011 episode of How On Earth.