Arrested phase separation in reproducing bacteria creates a generic route to pattern formation.

Area of Science:

• Microbiology
• Mathematical Biology
• Biophysics

Background:

• Microbial populations exhibit complex behaviors, including pattern formation.
• Density-dependent motility is a key factor influencing microbial spatial distribution.
• Existing models often struggle to explain stable patterns in reproducing populations.

Purpose of the Study:

• To present a generic mechanism for pattern formation in reproducing microorganisms.
• To investigate the role of density-dependent diffusivity in microbial self-organization.
• To model and understand arrested nonequilibrium phase separation in microbial systems.

Main Methods:

• Formulation of a mathematical model for run-and-tumble bacteria.
• Analysis of density-dependent diffusivity and its impact on population dynamics.
• Comparison of model predictions with observed microbial patterns.

Main Results:

• A generic mechanism for stable pattern formation driven by density-dependent diffusivity was identified.
• Arrested nonequilibrium phase separation leads to distinct dense and dilute microbial regions.
• Cell division in dilute regions and cell death in dense regions sustain the patterns.
• The model predicts patterns similar to those arising from chemotaxis, without assuming it.

Conclusions:

• Density-dependent diffusivity is sufficient to generate stable microbial patterns.
• The proposed mechanism offers a novel explanation for microbial self-organization.
• This work provides insights into microbial collective behaviors and spatial dynamics.