The Influence of Motility on Bacterial Accumulation in a Microporous Channel

TL;DR

This study uses molecular dynamics and lattice Boltzmann simulations to explore how bacterial motility influences their accumulation around obstacles in a porous channel, revealing the roles of flow, swimming behavior, and geometry.

Contribution

It introduces a detailed bacterial model incorporating hydrodynamics and run-and-tumble behavior to reproduce experimentally observed accumulation phenomena.

Findings

Bacteria accumulate on the rear side of obstacles under certain flow conditions.

Hydrodynamic interactions and motility significantly influence bacterial accumulation.

Channel geometry and wall interactions are crucial in bacterial distribution patterns.

Abstract

We study the transport of bacteria in a porous media modeled by a square channel containing one cylindrical obstacle via molecular dynamics simulations coupled to a lattice Boltzmann fluid. Our bacteria model is a rod-shaped rigid body which is propelled by a force-free mechanism. To account for the behavior of living bacteria, the model also incorporates a run-and-tumble process. The model bacteria are capable of hydrodynamically interacting with both of the channel walls and the obstacle. This enables the bacteria to get reoriented when experiencing a shear-flow. We demonstrate that this model is capable of reproducing the bacterial accumulation on the rear side of an obstacle, as has recently been experimentally observed by [G. L. Mino, et al., Advances in Microbiology 8, 451 (2018)] using E.coli bacteria. By systematically varying the external flow strength and the motility of the bacteria, we resolve the interplay between the local flow strength and the swimming characteristics that lead to the accumulation. Moreover, by changing the geometry of the channel, we also reveal the important role of the interactions between the bacteria and the confining walls for the accumulation process.