A flexible tail allows swimming bacteria to thin the surrounding liquid and to free themselves when trapped along walls or obstacles. This finding could influence how bacterial growth on medical, industrial, and agricultural surfaces is controlled. The new study by researchers at Penn State, published in a recent issue of the Royal Society journal Interface, used mathematical models to understand how bacteria with flagella—a collection of spinning hairs used for propulsion that act together like a tail—overcome forces from the flow of a liquid and navigate complex environments.