Internal chemical gradients coupled to self-generated flows drive pattern formation in a cytoskeletal active fluid

Isabel Ruffin

Title: Internal chemical gradients coupled to self-generated flows drive pattern formation in a cytoskeletal active fluid

Abstract: In cells, material reorganization is often driven by patterned chemical gradients. We have created a simplified system to investigate the coupling between spatial distributions of energy sources and energy-consuming active material flows. Our model system is a microtubule-based active fluid, and we embed enzyme-coated beads as sources of fuel to locally activate the fluid. As the beads are advected by the microtubule flows they generate, the feedback between spatial fuel gradients and active flows generate spatiotemporal patterning. We quantify system dynamics using PIV and particle tracking on fluorescently labeled microtubules and beads. The system dynamics are controlled by varying the bead concentration. At high bead concentrations, activity is mostly homogeneous through the system with short-lived fluctuations in local microtubule density. At low bead concentrations, active flows are localized around each individual bead with nontrivial deformations in the microtubule fluid. At intermediate bead concentrations, collective flows generated by the beads result in emergent large-scale microtubule structures that grow and shrink with time.