There was an interesting story posted on Popular Science, specifically their BeerSci series. They did a great job of spinning the story as a love story, albeit an unusual one between fruit flies and brewer’s yeast, especially since the original title of the study they’re reporting on was The Fungal Aroma Gene ATF1 Promotes Dispersal of Yeast Cells through Insect Vectors. But it is, and in How Flies Are Responsible For Beer’s Tasty, Fruity Smells, they detail how,”[i]n a series of experiments, biologists from several institutes in Belgium demonstrated that brewer’s yeast makes fruity, floral smells to attract fruit flies. In the wild, yeast might live on rotting fruit and entice flies to come to them there. Yeast and flies’ relationship benefits them both, the biologists found. Previous studies have found that eating yeast helps fruit fly larva develop faster and survive better. This new study found that fruit flies help spread yeast to new environments, like a bee spreading pollen.” In effect, their study demonstrates “the co-evolution of two species.”

Here’s the summary from the original, published in Cell Reports.

Yeast cells produce various volatile metabolites that are key contributors to the pleasing fruity and flowery aroma of fermented beverages. Several of these fruity metabolites, including isoamyl acetate and ethyl acetate, are produced by a dedicated enzyme, the alcohol acetyl transferase Atf1. However, despite much research, the physiological role of acetate ester formation in yeast remains unknown. Using a combination of molecular biology, neurobiology, and behavioral tests, we demonstrate that deletion of ATF1 alters the olfactory response in the antennal lobe of fruit flies that feed on yeast cells. The flies are much less attracted to the mutant yeast cells, and this in turn results in reduced dispersal of the mutant yeast cells by the flies. Together, our results uncover the molecular details of an intriguing aroma-based communication and mutualism between microbes and their insect vectors. Similar mechanisms may exist in other microbes, including microbes on flowering plants and pathogens.

You can also read the entire study as a pdf, but to get a sense of what it all means, read Francie Diep’s How Flies Are Responsible For Beer’s Tasty, Fruity Smells and keep in mind her warning from the outset. “Sorry, but brewer’s yeast did not evolve for you.” Perhaps not, but at least we can still reap the benefits of the relationship between those fruit flies and the yeast used to create delicious beer.