Microdomains and Stress Distributions in Bacterial Monolayers on Curved Interfaces

TL;DR

This study uses simulations to explore how curvature affects the organization and stress distribution in bacterial monolayers, revealing that curvature and cell shape influence alignment and stress localization.

Contribution

It provides new insights into how surface curvature impacts the organization and stress patterns in bacterial monolayers, extending active nematic physics to biological systems on curved interfaces.

Findings

Alignment increases with cell aspect ratio.

Alignment decreases with surface curvature.

Stress concentrates in low-order regions of the monolayer.

Abstract

Monolayers of growing non-motile rod-shaped bacteria act as active nematic materials composed of hard particles rather than the flexible components of other commonly studied active nematics. The organization of these granular monolayers has been studied on flat surfaces but not on curved surfaces, which are known to change the behavior of other active nematics. We use molecular dynamics simulations to track alignment and stress in growing monolayers fixed to curved surfaces, and investigate how these vary with changing surface curvature and cell aspect ratio. We find that the length scale of alignment (measured by average microdomain size) increases with cell aspect ratio and decreases with curvature. Additionally, we find that alignment controls the distribution of extensile stresses in the monolayer by concentrating stress in low-order regions. These results connect active nematic physics to bacterial monolayers and can be applied to model bacteria growing on droplets, such as marine oil-degrading bacteria.