Active matter from living polymers: The FtsZ paradigm

This review reframes the bacterial cytokinetic protein FtsZ as a living-polymer route to motor-free active matter whose mechanical output is active stress rather than directed stepping. FtsZ, a tubulin homolog, self-assembles into dynamic treadmilling filaments that consume GTP to inject stress into soft environments and, through interfacial coupling, bias deformation and flow. Experiments across interfaces (membrane-bound assemblies, monolayers) and bulk composites (polymer matrices of hydrogels) show that turnover-driven activity can produce extensile remodeling, strain-dependent softening, and activity-controlled fluidization, with mechanical polarity selected by confinement and boundary conditions. On the theory side, ideas from polymer physics, lever-like geometric transduction, instability and bifurcation frameworks, and soft glassy rheology connect filament turnover to emergent metamaterial response, including regimes of negative mechanical susceptibility. Together, these advances position FtsZ as a minimal, biochemically tunable actuator for designing reconfigurable nonequilibrium mechanics in active soft materials and biohybrid matter.