Fruit flies can taste the bacteria in food


Fruit flies have a taste for rotten fruit, but they avoid eating and laying eggs in contaminated food. Professor Talavera and his colleagues have shown that a receptor called TRPA1 enables fruit flies to detect harmful bacteria and thus avoid infections. The findings have potential for insect pest control.

Our immune system fights infections, but it’s much more efficient to avoid the bacteria that can make us sick. Our senses help us do that: we know better than to drink sour milk or eat suspicious-looking fish. Researchers from KU Leuven, VIB, and NERF have now shown that fruit flies, too, can detect pathogens in food with their sense of taste.

The researchers studied Drosophila fruit flies. These fruit flies feed on and lay eggs in rotten food, and overripe fruit in particular, which is a rich source of energy, proteins, and yeast. However, fruits may contain bacteria such as E.coli, which release a toxin that can be as harmful in fruit flies as it is in human beings.

“To find out whether fruit flies can detect bacteria,” Professor Karel Talavera explains, “we offered them two types of food: healthy food and food contaminated with E.coli. We discovered that the fruit flies tasted and then rejected the contaminated food. The females also refused to lay eggs on it. This shows that fruit flies have a specific mechanism to detect and avoid potentially dangerous food.”

Central to this mechanism is the activation of a protein called TRPA1, found in neurons in the lower jaw that detect bitter substances. In human beings, for instance, the activation of this protein is linked to the pungent taste of mustard, garlic, or wasabi. Professor Talavera continues: “When the TRPA1 receptor of fruit flies is removed, the flies eat the contaminated food and lay eggs in it. This tells us that the receptor is essential to protect fruit flies against infections and ensure their survival.”

The findings may help fight insect pests. Fruit flies are hardly dangerous, but other insects with a similar receptor may pose a threat to agriculture or spread diseases. Genetically modifying their receptor could increase these insects’ sensitivity to bacteria and thus facilitate their elimination.

Click here to read the study in eLife (open access)