Chaotic dynamics and oxygen transport in thin films of aerotactic bacteria

A kinetic model and three-dimensional numerical simulations are applied to study the dynamics in suspensions of run-and-tumble aerotactic bacteria confined in free-standing liquid films surrounded by air. In thin films, oxygen and bacterial concentration profiles approach steady states. In thicker films, a transition to chaotic dynamics is shown to occur and is characterized by unsteady correlated motions, the formation of bacterial plumes, and enhanced oxygen transport and consumption. This transition, also observed in previous experiments, arises as a result of the coupling between the aerotactic response of the bacteria and the flow fields they generate via hydrodynamic interactions.