Density-Dependent Transition in Bacterial Self-Organization Driven by Confinement and Aerotaxis

Minjun Kim; Joonwoo Jeong

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arXiv · 2603.14532

Density-Dependent Transition in Bacterial Self-Organization Driven by Confinement and Aerotaxis

Minjun Kim·Joonwoo Jeong

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Abstract

We experimentally investigate how aerotactic bacteria, confined within a thin liquid film between two solid substrates, respond to a controlled oxygen gradient. We find that the total bacterial number density dictates which mechanism dominates the steady-state spatial distribution: wall accumulation or aerotaxis. At low densities, despite receiving oxygen only from one substrate, motile bacteria accumulate at both walls, forming a symmetric distribution. In contrast, pronounced aerotactic migration toward the oxygen-supplying wall emerges as the density increases. Analyzing the temporal evolution of this bacterial distribution reveals that the aerotactic response is driven by a self-generated oxygen gradient induced by collective respiration. Our diffusion-advection model of bacteria and oxygen, accounting for aerotactic migration, hydrodynamic attraction to the walls, and respiration, quantitatively reproduces our experimental observations and provides valuable insights into bacterial self-organization within complex environments.

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Minjun Kim, Joonwoo Jeong. 2026-03-15. Density-Dependent Transition in Bacterial Self-Organization Driven by Confinement and Aerotaxis. https://arxiv.org/abs/2603.14532

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