It turns out that the common fruit fly – Drosophila Mengaster – with one of the most studied set of genes in biology, does something quite helpful for us.
Scientists have figured out that the fruit fly and our friend Saccharomyces cerevisiae (That would be naturally occurring yeast) have a symbiotic relationship. It turns out that yeast hitches a ride in the fruit fly’s gut, making it to plentiful supplies of sugar (e.g. overripe fruit) and, in turn, it ferments the sugars there and creates lots of aromatic chemicals that enable the fruit fly to find its way to more of the same fruit.
Actually, this is part of a chain of symbiotic relationships: you’ll remember that naturally occurring sourdough yeast works with bacteria – lactobacillus – to consume starches and sugars in wheat flour, and help us make some fine bread. One could argue that you and I are part of this chain too – if the yeast and bacteria didn’t help us make something tasty, I wouldn’t be helping both organisms reproduce and prolong their species.