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The Earth’s environment is full of reactive chemicals that can cause harm to organisms. One of the most common is hydrogen peroxide, which is produced by several bacteria in concentrations high enough to kill small animals, such as the roundworm Caenorhabditis elegans . Forced to live in close proximity to such perils, C. elegans have evolved defenses to ensure their survival, such as producing enzymes that can break down hydrogen peroxide. However, this battle is compounded by other factors. For instance, rising temperatures can increase the rate at which the hydrogen peroxide produced by bacteria reacts with the molecules and proteins of C. elegans . In 2020, a group of researchers found that roundworms sense these temperature changes through special cells called sensory neurons and use this information to control the generation of enzymes that break down hydrogen peroxide. This suggests that C. elegans may pre-emptively prepare their defenses against hydrogen peroxide in response to higher temperatures so they are better equipped to shield themselves from this harmful chemical. To test this theory, Servello et al. – including some of the authors involved in the 2020 study – exposed C. elegans to a species of bacteria that produces hydrogen peroxide. This revealed that the roundworms were better at dealing with the threat of hydrogen peroxide when growing in warmer temperatures. Experiments done in C. elegans lacking a class of sensory cells, the AFD neurons, showed that these neurons increased the roundworms’ resistance to the chemical when temperatures increase. They do this by repressing the activity of INS-39, a hormone that stops C. elegans from switching on their defense mechanism against peroxides. This is the first example of a multicellular organism preparing its defenses to a chemical after sensing something (such as temperature) that enhances its reactivity. It is possible that other animals may also use this ‘enhancer sensing' strategy to anticipate and shield themselves from hydrogen peroxide and potentially other external threats.
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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.
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- PAR ID:
- 10325917
- Editor(s):
- Weaver, Benjamin
- Date Published:
- Journal Name:
- PLOS Pathogens
- Volume:
- 17
- Issue:
- 12
- ISSN:
- 1553-7374
- Page Range / eLocation ID:
- e1010112
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1371/journal.ppat.1010112
