|CREDIT: by Barry Carlsen/University of Wisconsin-Madison|
This is a fascinating article about a real-life yeastie detective story. Apparently lager yeast is a hybrid - part ale yeast and part something else. But what something? No one knew - the genetic makeup was not native to Bavaria where lagers originated.
But now a University of Wisconsin researcher has found the missing link and not at all where you would expect it: Patagonia. From the LiveScience article:
A fruit fly's journey from Patagonia to Bavaria could be the reason we enjoy nice, cold-brewed lager beers today. The missing parent of the hybrid yeast used for brewing lagers has just been discovered in Patagonia.
Until now, scientists had known lager beers were made from a hybrid yeast, with half of its genes coming from a common ale yeast and the other half coming from an unknown species.
"Nothing they could find in the wild or in the freezer collections could match the missing component of the lager yeast," study researcher Chris Todd Hittinger at the University of Wisconsin-Madison, told LiveScience.
They found the missing yeast growing on southern beech trees in Patagonia. They sequenced the genes and found that this species of yeast was very likely to be a parent of the lager yeast hybrid.
"It’s a 99.5 percent match to the missing half of the lager genome. It's clear that it is this species," Hittinger said.
Each lager-yeast parent contributed one copy of its genome to the special yeast through sexual reproduction. The resulting yeast hybrids are sterile, meaning they can't reproduce sexually, but they can make direct copies of themselves and expand their genetically identical population.
In nature, this wouldn't be a smart evolutionary tactic, because it doesn't allow the yeast to adapt to changing conditions, the researchers said; but in the beer-brewing facilities, where temperatures are constant and food is freely available, the yeast can thrive.