Serotonin, a well-known neurotransmitter, is primarily produced in the gut, where it plays a crucial role in regulating bowel function via the enteric nervous system, often referred to as the "gut-brain." Recent research has shed light on the influence of gut microbiota on serotonin levels, but the specific capability of these bacteria to produce biologically active serotonin has remained unclear.
In a groundbreaking study published in Cell Reports, researchers have identified two bacterial species, Limosilactobacillus mucosae and Ligilactobacillus ruminis, that collaborate to synthesize serotonin. The team conducted experiments by introducing these bacteria into germ-free mice, which typically exhibit low serotonin levels. Following the introduction of the microbes, the mice showed increased serotonin levels in their intestines, an uptick in nerve cell count in the colon, and a normalization of gastrointestinal transit times.
Fredrik Bäckhed, a Professor of molecular medicine at Sahlgrenska Academy, University of Gothenburg, remarked, "It is incredibly fascinating how gut bacteria can produce bioactive signaling molecules that affect health."
The study also revealed that individuals with Irritable Bowel Syndrome (IBS) had significantly lower levels of L. mucosae in their stool samples compared to healthy subjects. This particular bacterium possesses the enzyme necessary for serotonin production, suggesting a potential link between gut health and serotonin synthesis.
Magnus Simrén, a Professor of medical gastroenterology at Sahlgrenska Academy, noted, "Our results indicate that certain intestinal bacteria can produce bioactive serotonin and thus play an important role in intestinal health, opening new avenues for treating functional gastrointestinal disorders such as IBS."
Bäckhed concluded, "Our findings suggest that intestinal bacteria can create signaling substances like serotonin, which may be pivotal in understanding how the gut and its microbiota influence our brain and behavior."
