Flies, Yeast, and Making Wine Published: April 30, 2018 By: Alli Quan Merlot grapes at a vineyard site. It happens to all of us. One moment, you’re enjoying a nice glass of wine and suddenly some fruit flies, who seem to have appeared out of thin air, have invited themselves to enjoy your wine with you. While it may seem like these flies are after your wine, they are actually searching for the yeast that helped produce wine. During the process of winemaking, yeast ferment sugars from grapes into alcohol and add fruity flavors into the finished wine product. These yeast smells are attractive to fruit flies, or Drosophila, because both adult and developing flies consume yeast as part of their diet. Alli Quan recording information on samples in a wine cellar. In nature, flies and yeast participate in a mutualistic relationship, meaning that they benefit each other. While Drosophila depend on yeast for nutrition, yeast cannot be dispersed by wind and depend on flies to cart them from one place to another. This relationship is so strong that Drosophila can accurately track periodic pulses of yeast aromas, explaining how they are able to find our wine so quickly! In my thesis work in Michael Eisen’s lab in the Department of Molecular and Cell Biology at UC Berkeley, I’ve strived to understand the fly-yeast mutualism in vineyards by characterizing the yeast species that are associated with Drosophila and identifying meaningful patterns to these associations. All of my collections take place in vineyards that use spontaneous fermentations, meaning that winemakers only use the yeast present on grapes at the time of harvest to produce wine. To make consistently great wine, winemakers rely on flies to bring yeasts to the grapes year after year. My collections have taken me to vineyards all over the Bay Area and allowed me to collaborate with and develop really great relationships with winemakers. They’ve taught me so much outside of what a molecular biologist might normally encounter in the lab, and I’ve developed a deep appreciation for the hard work and art that goes into winemaking. Not to mention that I get to spend summer and fall in some beautiful vineyards! Alli collecting Drosophila in wine fermentation tanks. To me, the most rewarding part of my thesis project has been the ability to share it with my local community. Wine is something many people can easily relate to and have an innate curiosity for. In the past, I’ve worked with the California Academy of Sciences to organize an interactive booth about yeast and wine at their NightLife events. With the help of my labmates, we discussed the role of yeast and flies in winemaking with museum visitors by making small batches of wine with different yeast species and allowing people to smell the differences between them. Making my science approachable and accessible to the public was a fun and rewarding challenge. I think it’s an important experience to have as a graduate student and, in my future career, I’m looking forward to more opportunities to interact with people who might not think about molecular biology on a daily basis. Alli and her lab mates presenting at Cal Academy’s “Wine NightLife” event. Overall, I’ve found that there is a broad range of yeast species that are suitable for Drosophila health, which is advantageous in a dynamic environment, such as a vineyard, where food sources and temperatures fluctuate throughout the year. Flies almost exclusively carry yeast species that are known to contribute fragrant aromas to wine and therefore flies are key contributors of yeast in spontaneous fermentations. Flies’ general attraction to yeast species help maintain a balanced and diverse fungal ecosystem in vineyards, subsequently producing wine with complex scents and flavors. So next time fruit flies join you for a glass of wine, be sure to thank them for their help! Allison Quan plans to complete her PhD in Molecular and Cell Biology in May 2018. With her training in genetics and microbiology, she is seeking positions in genetic testing, consumer goods, and science communication.