Kinesin-driven microtubule flows drive elastic structural transitions in actin networks

Active materials organize not just themselves but also their environment. Here, we describe how active consituents of a cytoskeletal composite material are reorganized into a steady-state structure through the action of molecular motors. We use fast-scanning three-dimensional confocal microscopy to directly image, at the resolution of single filaments, a network of actin as it undergoes structural reorganization due to the flow of kinesin-driven microtubule bundles. We examine the connected network structure as it evolves and connect structural transitions to changes in the elasticity of the network. Such work provides a basis for understanding how active fluids can sculpt passive materials into structures inaccessible via other means of construction.