Spatio-temporal patterns in Growing Bacterial Suspensions

TL;DR

This paper introduces a coarse-grained model for growing bacterial suspensions that captures the emergence of complex spatio-temporal patterns, including turbulence, as bacterial density increases.

Contribution

It develops a novel phenomenological model incorporating growth dynamics and hydrodynamics to explain pattern formation in bacterial suspensions.

Findings

Identification of four distinct phases: dilute, clustered, turbulent, and trapped.

Observation of vortex structures in the turbulent phase.

Model aligns with experimental observations of dense bacterial turbulence.

Abstract

The field of active matter explores the behaviors of self propelled agents out of equilibrium, with active suspensions, such as swimming bacteria in solutions, serving as impactful models. These systems exhibit spatio-temporal patterns akin to active turbulence, driven by internal energy injection. While bacterial turbulence in dense suspensions is well studied, the dynamics in growing bacterial suspensions are less understood. This work presents a phenomenological coarse-grained model for growing bacterial suspensions, incorporating hydrodynamic equations for bacterial density, orientation, and fluid velocity, with birth and death terms for colony growth. Starting with low density and random orientations, the model shows the development of local ordering as bacterial density increases. As density continues to rise, the model captures four distinct phases; dilute, clustered, turbulent, and trapped based on structural patterns and dynamics, with the turbulent phase characterized by spatio-temporal vortex structures, aligning with observations in dense bacterial suspensions.