Escherichia coli as a model active colloid: a practical introduction

TL;DR

This paper reviews how to control and measure the swimming behavior of Escherichia coli, providing protocols and methods to standardize experiments and use motility as a probe of cellular physiology.

Contribution

It offers a comprehensive review and practical protocol for maintaining consistent E. coli motility in experiments, facilitating reproducibility and physiological studies.

Findings

Established a protocol for constant-speed swimming of E. coli

Demonstrated motility as a high-throughput physiological probe

Provided methods to characterize colloidal and motile properties

Abstract

The flagellated bacterium Escherichia coli is increasingly used experimentally as a self-propelled swimmer. To obtain meaningful, quantitative results that are comparable between different laboratories, reproducible protocols are needed to control, `tune' and monitor the swimming behaviour of these motile cells. We critically review the knowledge needed to do so, explain methods for characterising the colloidal and motile properties of E.coli, cells, and propose a protocol for keeping them swimming at constant speed at finite bulk concentrations. In the process of establishing this protocol, we use motility as a high-throughput probe of aspects of cellular physiology via the coupling between swimming speed and the proton motive force.