Researchers have found that geosmin is made by certain kinds of bacteria that are known toxin producers. This acts as a warning to C. elegans, a common type of worm, that the bacteria they are about to graze on is poisonous. The chemical is an aposematic signal that triggers the blind worm's sense of taste just like a caterpillar's bright colors or a pufferfish's spines tell a sighted predator to stay away.
