Pattern formation in e. coli through negative chemotaxis: instability, condensation, and merging

TL;DR

This study combines experiments and mathematical modeling to understand how E. coli bacteria form and merge condensates through chemotaxis, revealing the dynamics across multiple time scales and the exponential decay of interactions.

Contribution

It introduces a modified Keller-Segel model that accurately predicts bacterial condensate formation, shape, and merging behavior under uniform stress conditions.

Findings

Experimental and model results agree on instability and condensate shapes.

Neighboring condensates coalesce over time due to chemotactic interactions.

Interaction forces decay exponentially with distance because of screening effects.

Abstract

Motile bacteria can migrate along chemical gradients in a process known as chemotaxis. When exposed to uniform environmental stress, Escherichia coli cells coordinate their chemotactic responses to form millimeter-sized condensates containing hundreds of thousands of motile cells. In this study, we combined experiments with mathematical modeling based on modified Keller-Segel equations to investigate the dynamics of this collective behavior across three distinct time scales: the shortest time scale, where spatial instability emerges; an intermediate time scale, where quasi-stationary bacterial condensates form; and finally, a longer time scale, during which neighboring bacterial accumulations coalesce. The model closely agrees with experimental results, quantitatively capturing the observed instability, the shape of mature condensates, and their coalescence dynamics. Specifically, we found that the force between neighboring bacterial accumulations decays exponentially with distance due to screening effects. We suggest that the model presented here could describe more broadly the dynamics of stress-induced condensation mediated by bacterial chemotaxis.