Gut Bacteria Consumes Neurochemical Linked To Depression

A recently-discovered strain of gut bacteria has been found to consume GABA, a neurochemical found in the brain. The neurotransmitter has a calming effect on the brain, and the bacteria’s reliance on GABA could explain how the microbiome has an effect on mood.

The bacterial species found in the gut – called KLE1738 – was found to grow in culture only when supplemented with GABA molecules. “Nothing made it grow, except GABA,” said Philip Strandwitz, a postdoctoral research associate from Northeastern University in Boston. Strandwitz and his colleagues presented their findings at the annual meeting of the American Society for Microbiology, in June.

This is the first time a bacterial species has been found which uses a neurotransmitter as an energy source. As GABA calms down brain activity by inhibiting signals between nerve cells, the researchers were surprised to find that it’s necessary for some microbial life.

Low levels of GABA have been linked to symptoms of depression and other mood disorders, further suggesting that the microbiome could have an influence on our brain. Another species of bacteria, Lactobacillus rhamnosus, was previously found to change the activity of GABA in mouse brains.

When researchers in the same study removed the vagus nerve in the mice, they found that the ability of the Lactobacillus rhamnosus to influence the GABA activity was diminished. Since the vagus nerve links the gut to the brain, the researchers postulated that it likely plays a role in the way in which the gut bacteria influence the brain.

Strandwitz and his colleagues are now studying the microbiome to identify any other bacteria that might consume, or produce, GABA. By studying the effects these microbes have on the brain, he hopes to eventually identify new treatments for depression, anxiety and other mood disorders.

“Although research on microbial communities related to psychiatric disorders may never lead to a cure, it could have astonishing relevance to improving patients’ quality of life,” said Domenico Simone of George Washington University in Ashburn, Virginia.