Beer has a fantastic aroma but a recent study has found the reason why it yields such a scent. The aroma's there to lure fruit flies, not people.

Researchers reporting in the journal, Cell Reports, discovered the yeast used to make beer evolved to secrete a scent that attracts fruit flies. In return, the flies benefit yeast by scattering their cells into the environment.

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Yeast produces small amounts of volatile compounds that give beer that pungent aroma somewhat related to ripening fruit. These compounds are highly appealing to fruit flies, which give the otherwise immobile yeast cells a ride to new food sources.

A gene called alcohol acetyl transferase (ATF1) is responsible for most of these fruity aromas.

Bioengineer Kevin Verstrepen accidentally made the discovery while studying in his lab 15 years ago. He was figuring out how yeast cells contribute to the flavor of both beer and wine when he left the two types of yeast he was working with on a bench.

Vestrepen returned to his lab after a weekend, only to find out a flask with a smelly yeast culture was infested by fruit flies that had managed to escape from a nearby genetics lab. The other flask that contained a mutation of a yeast strain in which ATF1 was deleted didn't have any flies on it.

Using a combination of molecular biology, behavioral tests and neurobiology, Verstrepen demonstrated that the loss of ATF1 changes the olfactory response of fruit flies and makes the yeast less appealing to them.

As expected, the mutated strain of yeast without ATF1 didn't benefit the yeast because the altered cells weren't dispersed by the fruit flies.

"Two seemingly unrelated species have developed an intricate symbiosis based on smell," Verstrepen said.

The study suggests species like microbes and insects team-up to benefit both parties by using evolving traits such as the sense of smell.

There is much to be learned about the mutualism between insects and microbes, which may have implications in agriculture and medicine, according to researchers.

TagsBeer, Fruit Fly