Yeast hitches a ride on beer-loving fruit flies

What do humans and flies have in common? A love of beer. We all know that people like (or even love) beer, but researchers think they’ve found the reason why it’s so tasty - for both humans and flies.

“The importance of yeast in beer brewing has long been underestimated. But recent research shows that the choice of a particular yeast strain or variety explains differences in taste between different beers and wines. In fact, yeasts may even be responsible for much of the ‘terroir’, the connection between a particular growing area and wine flavour, which previously often was attributed to differences in the soil,” said Kevin Verstrepen from VIB and KU Leuven.

Humans have harnessed the powers of yeast for thousands of years to produce beer, bread and wine. However, the role of yeast cells is more complex than just converting sugars into alcohol and carbon dioxide - they also produce flavour compounds that significantly contribute to the taste, flavour and overall quality of beer and wine.

A collaborative study led by scientists from VIB, KU Leuven and NERF shows that the fruity volatile compounds produced by yeast cells are highly appealing to fruit flies. The yeast cells use this to their advantage, hitching a ride to new food sources on the insects.

The researchers have narrowed this down to a key yeast gene - ATF1 - which, when deleted, means the fruit flies are no longer attracted to the scent. Moreover, the brain activity in flies that are exposed to yeasts without the ATF1 gene is very different from that of flies exposed to normal, fruity yeasts.

“Flies are strongly attracted to normal yeast cells, when compared to mutant yeasts that don’t produce esters. Knowing that esters make beer taste good, it seems that the same flavours that allow us to enjoy our beer probably evolved to attract flies and to help yeast disperse into broader ecosystems,” said Emre Yaksi (NERF - VIB/KU Leuven), the neuroscientist who led the experiments on flies.

The team believes that their findings have far-reaching implications. “We all know that flowers attract insects by producing aromas. But there’s also a lot of microbes living inside flowers, and the chemicals they produce may also play an important role,” said Joaquin Christiaens (VIB/KU Leuven), who performed the experiments with yeast cells.

Luis Franco (NERF - VIB/KU Leuven), who performed the fly assays, agrees. “There’s a lot to be learnt about the mutualism between insects and microbes, and some of what we find may have implications in agriculture and medicine. Don’t forget that insects also carry disease-causing microbes …”

The research will be published in the 23 October 2014 issue of Cell Reports.