Bacteria display optimal transport near surfaces -- bacteria as intermittent active chiral particles: trapped by hydrodynamics, escaping by adhesion

TL;DR

This study reveals how bacteria like EHEC use transient adhesion events to break surface-trapped circular swimming patterns, optimizing their surface exploration through a combined experimental and mathematical modeling approach.

Contribution

The paper introduces a data-driven mathematical model that explains how transient adhesion events regulate bacterial surface transport, a novel insight into bacterial motility behavior.

Findings

Stop-adhesion events occur at an optimal frequency for maximum surface diffusivity.

EHEC bacteria switch between circular trajectories and intermittent motion due to adhesion.

The model applies broadly to other bacterial strains and surfaces.

Abstract

The near-surface swimming patterns of bacteria are strongly determined by the hydrodynamic interactions between bacteria and the surface, which trap bacteria in smooth circular trajectories that lead to inefficient surface exploration. Here, we show by combining experiments and a data-driven mathematical model that surface exploration of enterohemorrhagic Escherichia coli (EHEC) -- a pathogenic strain of E. coli causing serious illnesses such as bloody diarrhea -- results from a complex interplay between motility and transient surface adhesion events. These events allow EHEC to break the smooth circular trajectories and regulate their transport properties by the use stop-adhesion events that lead to a characteristic intermittent motion on surfaces. We find that the experimentally measured frequency of stop-adhesion events in EHEC is located at the value predicted by the developed mathematical model that maximizes bacterial surface diffusivity. We indicate that these results and the developed model apply to other bacterial strains on different surfaces, which suggests that swimming bacteria use transient adhesion to regulate surface motion.