Gut Bacteria May Control Movement

A new study puts a fresh spin on what it means to “go with your gut.” The findings, published in Nature, suggest that gut bacteria may control movement in fruit flies and identify the neurons involved in this response. NINDS supported the research.

“This study provides additional evidence for a connection between the gut and the brain, and in particular outlines how gut bacteria may influence behavior, including movement,” said Dr. Margaret Sutherland, NINDS program director.

Researchers led by Dr. Sarkis Mazmanian, professor of microbiology at the California Institute of Technology, and graduate student Catherine Schretter, observed that germ-free flies, which did not carry bacteria, were hyperactive. For instance, they walked faster, over greater distances, and took shorter rests than flies that had normal levels of microbes. Mazmanian and his team investigated ways in which gut bacteria may affect behavior in fruit flies.

“Locomotion is important for a number of activities such as mating and searching for food. It turns out that gut bacteria may be critical for fundamental behaviors in animals,” said Mazmanian.

Fruit flies carry between 5 and 20 different species of bacteria and Mazmanian’s team treated the germ-free animals with individual strains of those microbes. When the flies received Lactobacillus brevis, their movements slowed down to normal speed. L. brevis was one of only two species of bacteria that restored normal behavior in the germ-free flies.

Mazmanian’s group also discovered that the molecule xylose isomerase, a protein that breaks down sugar and is found in L. brevis, may be critical to this process. Isolating the molecule and treating germ-free flies with it was sufficient to slow down the speedwalkers.