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 (H₂O₂) is the most common chemical threat that organisms face. Here, we show that H₂O₂ alters the bacterial food preference of Caenorhabditis elegans, enabling the nematodes to find a safe environment with food. H₂O₂ induces the nematodes to leave food patches of laboratory and microbiome bacteria when those bacterial communities have insufficient H₂O₂-degrading capacity. The nematode’s behavior is directed by H₂O₂-sensing neurons that promote escape from H₂O₂ and by bacteria-sensing neurons that promote attraction to bacteria. However, the input for H₂O₂-sensing neurons is removed by bacterial H₂O₂-degrading enzymes and the bacteria-sensing neurons’ perception of bacteria is prevented by H₂O₂. 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.