Stability and dynamics of anisotropically-tumbling chemotactic swimmers

TL;DR

This paper investigates how slight anisotropy in the tumbling behavior of micro-swimmers affects their collective pattern formation, revealing that anisotropy reduces aggregate size but can increase the number of aggregation peaks.

Contribution

It introduces the first analysis of the impact of tumbling anisotropy on chemotactic pattern formation using linear and nonlinear methods.

Findings

Anisotropy diminishes chemotactic aggregate magnitude.

Anisotropy can lead to more aggregation peaks.

Pattern formation is significantly affected by tumbling anisotropy.

Abstract

Micro-swimmers such as bacteria perform random walks known as run-and-tumbles to move up chemo-attractant gradients and as a result aggregate with others. It is also known that such micro-swimmers can self-organize into macroscopic patterns due to interactions with neighboring cells through the fluidic environment they live in. While the pattern formation resulting from chemotactic and hydrodynamic interactions separately and together have been previously investigated, the effect of the anisotropy in the tumbles of micro-swimmers has been unexplored. Here we show through linear analysis and full nonlinear simulations that the slight anisotropy in the individual swimmer tumbles can alter the collective pattern formation in non-trivial ways. We show that tumbling anisotropy diminishes the magnitude of the chemotactic aggregates but may result in more such aggregation peaks.