Trillions of microbes inhabit the human gastrointestinal tract and are known to influence metabolism and immunity. However, relatively little is known about how these organisms influence the behavior of their host. As gut bacteria participate in digestion, they alter the levels of macromolecules, such as carbohydrates, within the gut and produce neuromodulators as byproducts. Due to their participation in energy-availability within the host, we hypothesized that gut bacteria play a role in locomotion. We have found significant differences between the locomotive behavior of adult flies without a microbiota (axenic) and those with a full microbiota (conventional). Mono-colonization studies have revealed that specific bacteria and, in particular, a bacterially-derived molecule influences a fly’s gait, speed, and activity levels. Through administering antibiotics and performing later colonization time points, we have also found that these effects are not due to changes during development. Neither mass, glucose, nor the IMD (Immune Deficiency) pathway has been found to mediate these effects on locomotion.
Our results reveal that the bacterial composition of the gut and its metabolic products are an important modulator of host locomotion. Locomotion is a behavior critical for the survival of an organism and is part of the progression of certain disease states. When combined with our results, this suggests that the gut microbiota is an important factor to consider in a variety of neural pathways and their behavioral outputs.