Mit study identifies molecules that let gut neurons detect bacteria
Researchers at the Massachusetts Institute of Technology have identified the molecular signals that allow gut neurons to distinguish between beneficial and harmful bacteria. The work reveals a chemical communication system between microbes and the nervous system that may also exist in humans. The findings, published in Current Biology in April 2026, provide a mechanistic basis for understanding how gut bacteria can influence brain function and behavior.
The study, conducted at the Picower Institute for Learning and Memory, used the nematode Caenorhabditis elegans, a transparent worm that feeds exclusively on bacteria. Researchers exposed the worms to 20 bacterial species and systematically broke down each microbe into its chemical components to identify what the gut neurons detect. DNA, lipids, proteins, and simple sugars showed no effect. Complex carbohydrate structures known as polysaccharides, which coat bacterial surfaces, triggered a strong neuronal response.
The team found that in Gram-positive bacteria, the cell wall component peptidoglycan strongly activated a key gut neuron known as NSM. When this neuron detected bacterial polysaccharides through acid-sensing ion channels, or ASICs, it released serotonin. This signal increased feeding rates and reduced movement, allowing the worm to remain in place and consume food efficiently. When researchers genetically disabled the ASIC channels, both the neuronal activation and the behavioral changes disappeared, confirming a direct molecular pathway linking bacterial detection to behavior.
The study also uncovered a built-in danger signal. The pathogen Serratia marcescens exists in pigmented and non-pigmented forms. Strains producing the red compound prodigiosin were significantly more lethal to the worms. In the presence of this molecule, the NSM neuron failed to activate and the worms stopped feeding. Adding prodigiosin to otherwise harmless bacteria suppressed the normal feeding response, indicating that the organism uses a specific chemical cue as an early warning system against harmful microbes.
Researchers say the findings may extend to human biology. ASIC channels identified in the study are similar to those found in human neurons, suggesting that comparable gut-brain signaling pathways could operate across species. The human gut microbiome has been linked to conditions such as depression and Parkinson’s disease, yet the underlying mechanisms remain unclear. By identifying precise molecular interactions between bacteria and neurons, the study opens the way for targeted therapies or dietary interventions designed to influence these pathways and improve health outcomes.
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