Serotonin produced by gut bacteria provides hope for a novel IBS treatment

Research from the University of Gothenburg, Sweden, clarifies the complex interaction between gut bacteria and irritable bowel syndrome (IBS).

Experiments demonstrate that gut bacteria can produce the important substance serotonin. The finding may lead to future treatments.

Researchers have identified two bacteria that together can produce serotonin: Limosilactobacillus mucosae and Ligilactobacillus ruminis.

When the bacteria were introduced into germ-free mice with serotonin deficiency, the levels of serotonin in the gut increased, as did the density of nerve cells in the colon. The bacteria also normalized the intestinal transit time.

The researchers were also able to see that people with IBS had lower levels of one of the bacteria (L. mucosae) in their stools compared to healthy individuals, and that this bacterium also has the enzyme required for serotonin production.

"It is incredibly fascinating how the gut bacteria can produce bioactive signaling molecules that affect health," says Fredrik Bäckhed, Professor of molecular medicine at Sahlgrenska Academy at the University of Gothenburg, and one of the leading authors of the study.

Image source: Moretti et al. (2025), Cell Reports.