Modulation of sensory perception by hydrogen peroxide enables Caenorhabditis elegans to find a niche that provides both food and protection from hydrogen peroxide

Hydrogen peroxide (H ₂ O ₂ ) is the most common chemical threat that organisms face. Here, we show that H ₂ O ₂ alters the bacterial food preference of Caenorhabditis elegans , enabling the nematodes to find a safe environment with food. H ₂ O ₂ induces the nematodes to leave food patches of laboratory and microbiome bacteria when those bacterial communities have insufficient H ₂ O ₂ -degrading capacity. The nematode’s behavior is directed by H ₂ O ₂ -sensing neurons that promote escape from H ₂ O ₂ and by bacteria-sensing neurons that promote attraction to bacteria. However, the input for H ₂ O ₂ -sensing neurons is removed by bacterial H ₂ O ₂ -degrading enzymes and the bacteria-sensing neurons’ perception of bacteria is prevented by H ₂ O ₂ . The resulting cross-attenuation provides a general mechanism that ensures the nematode’s behavior is faithful to the lethal threat of hydrogen peroxide, increasing the nematode’s chances of finding a niche that provides both food and protection from hydrogen peroxide.