Scientists discover gut bacteria that influences mood by 'eating' brain chemical

For the first time, scientists have determined that there are bacteria in the human gut which depend on chemicals from our brain for survival. The discovery of this relationship between the gut biome and brain chemistry could lead the way to new treatments for depression and a host of other disorders.

New Scientist said Friday that scientists at Boston's Northeastern University have isolated a group of bacteria that depend upon the brain chemical gamma-aminobutyric acid or GABA -- a molecule that the brain uses to calm itself -- to survive.

Researcher Philip Strandwitz explained that the fact that the newly discovered bacteria -- named KLE1738 -- appear to eat GABA to live could explain the newly emerging link between gut microbiome health and mental health.

A biome is any system that contains living organisms like a stretch of wetlands or a terrarium in a science class. The microbiome is the teeming mass of 100 trillion bacteria that live inside each person.

The Northwestern group isolated KLE1738 and tried to ascertain what its role was among the hundreds of species of bacteria that make up the microbiome.

In a presentation last month at the annual meeting of the American Society for Microbiology in Boston, Strandwitz said, "Nothing made it grow, except GABA."

New Scientist said, "GABA acts by inhibiting signals from nerve cells, calming down the activity of the brain, so it’s surprising to learn that a gut bacterium needs it to grow and reproduce. Having abnormally low levels of GABA is linked to depression and mood disorders, and this finding adds to growing evidence that our gut bacteria may affect our brains."

A separate study found in 2011 that the bacteria Lactobacillus rhamnosus dramatically altered brain activity in laboratory mice, particularly levels of GABA. Mice with high amounts of Lactobacillus rhamnosus handled stress more effectively. When researchers surgically removed the mice's vagus nerve -- which connects the gut to the brain -- the effect vanished, leading researchers to conclude that the nerve plays a role in mood regulation and conveying signals between neurons in the brain and the gut.

Strandwitz hopes to expand the team's research to find bacteria that consume or even produce GABA, as well as to study the chemical's effects on behavior and emotional wellbeing.

Other scientists, like Domenico Simone of George Washington University in Ashburn, Virginia, agree that the line of study could be a boon to the treatment of depression and anxiety.

“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 Simone.