Tomorrow on NPR’s Science Friday the show they’ll be airing is called “The Evolution of Beer,” but really it’s yeast they’ll be talking about. Here’s the description of the show:

In the world of beer, ales are separated from lagers by their yeast. Lager yeast collects on the bottom of the fermenting vessel and ferments sugars into alcohol at lower temperatures that ale yeast, which operates at higher temperatures at the top of the fermentation vat. In new research published this week in the journal Genome Research, scientists examined the genetic sequences of 17 unique lager yeast strains from breweries in Europe and North America, tracing variations in the genetic code of those yeasts back through time. The researchers found that a key hybridization step, in which genetic information from two different yeasts combined and rearranged to yield a new ‘lager yeast’ organism, may have actually happened twice. The researchers found two different family groupings in the lager yeasts they studied, with one lineage associated primarily with Carlsberg breweries in Denmark and breweries in what is now Czechoslovakia, and the other family grouping connected mainly to breweries in the Netherlands, including Heineken. In this segment, we’ll talk with one of the authors of the study about genetics and beer, and about the genes behind lager beer styles such as Pilsners, Märzen, Dortmunders, and Bocks.

Also, according to a report on the study on New Scientist, “Lagers belong to two main families: the Saaz group such as Carlsberg, brewed in Denmark; and the Frohberg lagers that include Heineken and Oranjeboom from the Netherlands.” To discover this, the team examined seventeen yeast strains from around the word and used from 1883 to 1976.

Also from New Scientist:

It has long been thought that Saccharomyces pastorianus, the yeast used in lager production, formed only once from the hybridisation of S. cerevisiae and S. bayanus. Instead, the team discovered that it happened at least twice in two separate locations in Europe, giving rise to the two different lager families. The hybrid, which makes lager instead of ale, probably evolved in Bavarian beer-brewing cellars during the 16th century.

The team also found that Saaz yeasts have a single copy of each parent yeast’s genome, whereas the Frohberg yeasts have an extra copy from S. cerevisiae. They believe this difference affects the flavour of the lager, as well as how quickly the yeasts can ferment the hops.

Sounds like that should be a pretty interesting show. From looking at their schedule, it looks like the whole Friday will be devoted to genes, with the beer only part of the day’s topics. Check your local NPR radio station for when it will air in your part of the world. In the Bay Area, KQED (88.5) will air it at 11:00 a.m. tomorrow.