Large-scale vortex lattice emerging from collectively moving microtubules

Area of Science:

• Physics
• Biophysics
• Soft Matter Physics

Background:

• Spontaneous collective motion is an emergent phenomenon observed in nature, like bird flocks and fish schools.
• Theoretical models for collective motion lack experimental verification, especially in biological systems with many variables.
• Subcellular scale in vitro experiments offer controlled environments to test theoretical ideas.

Purpose of the Study:

• To investigate the mechanisms of collective motion in a controlled in vitro system.
• To experimentally verify theoretical predictions regarding emergent phenomena.
• To explore self-organization and pattern formation in biological filament systems.

Main Methods:

• Experiments using microtubules propelled by surface-bound dynein molecular motors.
• Observation of microtubule interactions and collective behaviors at high densities.
• Utilizing a mathematical model to verify the observed emergent structures.

Main Results:

• Colliding microtubules exhibit a high probability of aligning with each other (nematic alignment).
• At high densities, microtubules self-organize into vortices (around 400 µm diameter) with circulating motion.
• Vortices form a lattice structure over longer timescales, driven by local interactions and microtubule motion.

Conclusions:

• The study demonstrates emergent collective motion and self-organization in a simplified biological system.
• Observed phenomena result from local interactions and individual microtubule dynamics, not long-range forces.
• Findings suggest new universality classes for collective motion and have implications for biological structures.