Differential Dynamic Microscopy of Bacterial Motility

TL;DR

This paper introduces differential dynamic microscopy (DDM) as a rapid, high-throughput method for analyzing bacterial motility, providing accurate measurements of swimming speeds and motile fractions in E. coli suspensions.

Contribution

The study demonstrates DDM's effectiveness for characterizing active particle dynamics, offering a faster alternative to traditional tracking methods with high accuracy.

Findings

DDM accurately measures swimming speed distributions.

The fraction of motile cells can be reliably quantified.

Non-motile cell diffusivity increases with motile cell concentration.

Abstract

We demonstrate 'differential dynamic microscopy' (DDM) for the fast, high throughput characterization of the dynamics of active particles. Specifically, we characterize the swimming speed distribution and the fraction of motile cells in suspensions of Escherichia coli bacteria. By averaging over ~10^4 cells, our results are highly accurate compared to conventional tracking. The diffusivity of non-motile cells is enhanced by an amount proportional to the concentration of motile cells.