Bacteria and human cells break symmetry in collective motion

Researchers at Ben‑Gurion University of the Negev (BGU) have published a study in Nature Physics that shows living systems can violate established physical symmetry rules when collective cellular flows emerge and collapse. The work focuses on how groups of motile cells—specifically single‑cell bacteria and human respiratory epithelial cells—organize into dynamic patterns that spontaneously break mirror symmetry.

By tracking the motion of individual cells within these groups, the team found that the cells follow curved, irreversible spiral trajectories rather than the straight or symmetric paths predicted by conventional liquid‑crystal models. This behavior indicates that biological activity can generate intrinsic chirality, a property not accounted for in traditional theories of active matter. The findings suggest that the physics of living systems may require new theoretical frameworks that incorporate the inherent asymmetry of cellular motion.

The study broadens our understanding of how biological organization can defy classical symmetry principles, potentially informing future research in soft matter physics, microbiology, and the design of synthetic active materials.