Self-Sustained Density Oscillations of Swimming Bacteria Confined in Microchambers

TL;DR

This study numerically investigates how confined swimming bacteria exhibit self-sustained density oscillations and circulating flows due to channel geometry and density-dependent motility.

Contribution

It reveals the mechanisms behind oscillatory and circulating behaviors of bacteria in microchambers, highlighting the role of channel narrowness and density-dependent motility.

Findings

Oscillatory pumping state with periodic filling of chambers.

Circulating flow state maintaining constant population levels.

Density-dependent motility influences bacterial dynamics.

Abstract

We numerically study the dynamics of run-and-tumble particles confined in two chambers connected by thin channels. Two dominant dynamical behaviors emerge: (i) an oscillatory pumping state, in which particles periodically fill the two vessels and (ii) a circulating flow state, dynamically maintaining a near constant population level in the containers when connected by two channels. We demonstrate that the oscillatory behaviour arises from the combination of a narrow channel, preventing bacteria reorientation, and a density dependent motility inside the chambers.