Self-enhanced mobility enables vortex pattern formation in living matter

Area of Science:

• Active Matter Physics
• Biological Self-Organization
• Microbiology

Background:

• Living systems exhibit self-organized structures from subcellular to organismal levels.
• Biological pattern formation often relies on chemical signaling, but physical interactions can also drive order.

Purpose of the Study:

• To discover a new physical mechanism for self-organized pattern formation in dense bacterial systems.
• To investigate the emergence of large-scale spatial structures driven by physical interactions.

Main Methods:

• Observation of dense bacterial suspensions.
• Single-cell tracking analysis.
• Numerical simulations.

Main Results:

• Dense bacterial living matter spontaneously formed a centimeter-scale lattice of mesoscale, fast-spinning vortices.
• Each vortex contained 10^4-10^5 motile bacterial cells with hexagonal order.
• Cellular self-enhanced mobility, driven by collective stresses, enabled this pattern formation.

Conclusions:

• Self-enhanced mobility provides a simple physical mechanism for pattern formation in living systems.
• This finding is relevant to active matter systems near the fluid-solid transition.