New Insights into the Dynamics of Swarming Bacteria: A Theoretical Study

TL;DR

This theoretical study models the two-dimensional dynamics of swarming E. coli bacteria, demonstrating how agent interactions and modified run-and-tumble behavior lead to emergent swarming patterns.

Contribution

It introduces a simulation model that reproduces experimental swarming behavior by adjusting agent interactions and tumble dynamics.

Findings

Densely packed agents exhibit swarming behavior due to collisions.

Modified run-and-tumble dynamics can produce swarming without active turning.

Simulations align with experimental measurements of E. coli movement.

Abstract

In the present work we simulate the basic two-dimensional dynamics of swarming E. coli bacteria on the surface of a moderately soft agar plate. Individual bacteria are modelled by self-propelled ridged bodies (agents), which interact with each other only through inelastic collision and with the highly viscous environment through damping forces. The motion of single agents is modelled closely corresponding to the behaviour of swimming bacteria. The dynamics of the model were adjusted to reproduce the experimental measurements of swimming E. coli K 12. Accordingly, simulations with loosely packed agents (p=0) show typical run-and-tumble statistics. In contrast, simulations with densely packed agents (p=0.3-0.7) are dominated by interactions (collisions) between agents which lead to the emergence of swarming behaviour. In addition, we model the motion of single agents on the base of modified run-and-tumble dynamics, where the bacteria do not turn actively during the tumble. We show that simulations with densely packed modified agents lead as well the emergence of swarming behaviour, if rotational diffusion is considered.