Biofilms as self-shaping growing nematics

Area of Science:

• Soft Matter Physics
• Biophysics
• Materials Science

Background:

• Active nematics are nonequilibrium systems exhibiting emergent behavior driven by energy consumption.
• Their ordering and dynamics are sensitive to boundary conditions, similar to passive liquid crystals.
• Active nematics can potentially regulate their boundaries via self-generated stresses.

Purpose of the Study:

• To investigate how three-dimensional living nematics actively shape boundaries and regulate internal architecture.
• To model bacterial biofilms confined by hydrogels as a system for studying growth-induced stresses.
• To understand the relationship between boundary evolution, stress anisotropy, and emergent properties like cell ordering and topological defects.

Main Methods:

• Utilized bacterial biofilms confined within a hydrogel as a model system.
• Observed shape transitions (domes to lenses) influenced by environmental stiffness and cell-substrate friction.
• Developed a theoretical model incorporating confinement and interfacial forces to explain shape transitions.

Main Results:

• Demonstrated active boundary shaping and internal architecture regulation through growth-induced stresses in living nematics.
• Identified a sharp transition in biofilm shape correlating with environmental changes.
• Showed that boundary evolution and stress anisotropy dictate cell orientation and topological defect emergence.

Conclusions:

• Living nematics can actively control their boundaries and internal organization via growth-induced stresses.
• Biofilm shape transitions are governed by a balance between confinement and interfacial forces.
• Findings offer insights for engineering microbial consortia with programmable material properties.