Broken detailed balance at mesoscopic scales in active biological systems

TLDR

Living systems operate far from thermodynamic equilibrium at the molecular scale, yet how these nonequilibrium dynamics manifest at the cellular level remains unclear, as imbalanced transitions violate detailed balance. The authors employ video microscopy and statistical thermodynamics to pinpoint cellular‑scale fluctuations that violate detailed balance. They demonstrate that nonequilibrium dynamics are evident in the periodic beating of flagella and the irregular fluctuations of primary cilia. Battle et al., Science, this issue p.

Abstract

Identifying nonequilibrium dynamics Living systems clearly operate out of thermodynamic equilibrium at the molecular scale. How these activities are manifest at the cellular scale, however, has been unclear. Battle et al. use video microscopy together with statistical thermodynamics to unambiguously identify which random fluctuations at the cellular scale are out of equilibrium (see the Perspective by Rupprecht and Prost). Transitions between states obey a detailed balance in equilibrium, whereas imbalanced transitions point to nonequilibrium dynamics. For instance, nonequilibrium dynamics can be identified in the periodic beating of a flagellum and in the nonperiodic fluctuations of primary cilia. Science , this issue p. 604 ; see also p. 514