Spontaneous body wall contractions shape and stabilize the symbiotic microbiota

Rhythmic spontaneous contractions of body walls, such as those of the gastrointestinal tract, are a ubiquitous phenomenon in the animal kingdom. Studies in mice and humans have implied that intestinal dysmotility is associated with a disturbed microbiota, but the causal relationship has been unclear. Here, by applying experimental, flow physics and mathematical modelling approaches in the model Hydra, we provide functional evidence that reducing the frequency of spontaneous body wall contractions alters the fluid microenvironment near the tissue surface and thereby modifies the composition of the colonizing microbiota. Our findings suggest that spontaneous contractions of body walls enhance the transport of chemical compounds from and to the tissue surface where the bacteria reside, thus shaping and stabilizing the host-microbe associations.