Fast-moving bacteria self-organize into active two-dimensional crystals of rotating cells

Area of Science:

• Microbiology
• Biophysics
• Fluid Dynamics

Background:

• Thiovulum majus are among the fastest-swimming bacteria.
• Bacteria can exhibit complex collective behaviors when interacting.

Purpose of the Study:

• To investigate the collective dynamics of Thiovulum majus.
• To understand the formation of hexagonal bacterial lattices.

Main Methods:

• Observation of bacterial self-organization on a surface.
• Derivation of equations of motion based on hydrodynamic and steric interactions.

Main Results:

• Thiovulum majus spontaneously form 2D hexagonal lattices of rotating cells.
• Cellular rotation generates tornadolike flows, influencing neighbor positions.
• Intercellular forces lead to crystal rotation and reorganization.

Conclusions:

• Hydrodynamic and steric interactions govern the observed collective bacterial dynamics.
• The derived model explains key aspects of the active crystal behavior.
• The stability of these self-organized bacterial structures is discussed.