4 Minutes
Researchers at the University of Gothenburg have identified gut bacteria capable of producing serotonin — a discovery that reshapes our understanding of the gut-brain dialogue and points to new possibilities for treating irritable bowel syndrome (IBS). Scientists have uncovered a surprising link between specific gut bacteria and the body’s production of serotonin, a molecule essential for regulating intestinal activity.
Microbes, serotonin and the gut: what the study found
Serotonin is commonly discussed as a brain neurotransmitter, but more than 90% of the body's serotonin is actually made in the digestive tract where it controls muscle contractions, secretion, and sensation via the enteric nervous system — the so-called "second brain." Previous work suggested gut microbes influence host serotonin levels, but direct microbial production of active serotonin had not been demonstrated clearly in mammals.
In experiments reported in Cell Reports, investigators isolated two bacterial species that together produce bioactive serotonin: Limosilactobacillus mucosae and Ligilactobacillus ruminis. When researchers introduced these strains into germ-free mice with low serotonin levels, gut serotonin rose, nerve-cell density in the colon improved, and intestinal transit times normalized. Those functional changes tie the microbial activity to measurable physiological outcomes, not just biochemical signatures.
Why this matters for IBS and patient care
IBS is a heterogeneous disorder marked by abdominal pain and altered bowel habits (constipation, diarrhea, or both) and affects more women than men. While the causes of IBS are multifactorial — involving diet, motility, immune signaling and the microbiome — serotonin signaling is a central player because it directly regulates gut motility and sensitivity.
The Gothenburg team found that stool from people with IBS had lower levels of L. mucosae compared with healthy controls. L. mucosae also carries the enzyme machinery needed to synthesize serotonin, which raises the intriguing possibility that reduced abundance of this species contributes to serotonin deficiency in some patients.
"It is incredibly fascinating how the gut bacteria can produce bioactive signaling molecules that affect health," said Fredrik Bäckhed, Professor of molecular medicine at Sahlgrenska Academy, summarizing the broader significance. Magnus Simrén, Professor of medical gastroenterology at the same institution, added that the discovery opens new therapeutic avenues for functional gastrointestinal disorders such as IBS.
From bench to bedside: potential therapies and next steps
The immediate implications are scientific: we now know specific gut bacteria can synthesize a key host signaling molecule. Translationally, this suggests two promising routes for future interventions. One is microbial restoration — using targeted probiotics or defined bacterial consortia to reintroduce serotonin-producing strains. The other is leveraging the enzymes or metabolites these bacteria produce to design small-molecule or biotherapeutic approaches that modulate serotonin signaling locally in the gut.
But several steps remain before clinical application. Researchers need to confirm safety and efficacy in humans, identify which patient subgroups might benefit, and determine optimal dosing and delivery strategies. It’s also important to understand how diet, antibiotics, and other microbes shape the presence and activity of L. mucosae and L. ruminis in diverse populations.
Scientific context and open questions
This study contributes to a growing literature on microbe-host chemical communication. It highlights a more active role for microbes — not only modulating host pathways indirectly, but directly synthesizing bioactive molecules that participate in host physiology. Key open questions include how widespread serotonin-producing bacteria are across human populations, how stable their colonization is, and whether manipulating them alters extra-intestinal outcomes such as mood or pain perception via gut-brain signaling.
For people with IBS, these findings are cause for cautious optimism: restoring specific microbial functions rather than broadly altering the microbiome may yield more targeted, tolerable therapies. Imagine a future pill or live biotherapeutic that replenishes missing microbial serotonin production and eases symptoms without systemic side effects.
Source: scitechdaily
Comments
bioNix
wow, microbes making serotonin? mind blown. if this pans out could be huge for IBS patients, but curious how diet affects it and safety tho
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