Ethanol is a particularly cool molecule. It’s a solvent, which means lots of different molecules that don’t dissolve in water will dissolve in a solution of ethanol. It’s odorless, colorless, and it burns really well—a sign of a good fuel. It’s also a potent microbicide. When yeasts squirt it into their environment, it kills off local bacterial and fungal competition. Now, yeasts can actually reverse that part of their metabolism—they can slurp back up the ethanol they’ve made to use as an energy source, as food. It’s like a car running on its own exhaust—in times of emergency, yeasts can live
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