Differential Dynamic Microscopy: a High-Throughput Method for Characterizing the Motility of Microorganism

TL;DR

This paper introduces a rapid, high-throughput microscopy-based method that analyzes intensity fluctuations to characterize microorganism motility in 3D without tracking individual cells, enabling efficient analysis of large populations.

Contribution

The method provides a novel approach to quantify microorganism motility by analyzing spatio-temporal intensity fluctuations, validated with simulations and applicable to different microorganisms.

Findings

Successfully characterized E. coli swimming speed distribution and motile fraction.

Determined C. reinhardtii's swimming speed, oscillation amplitude, and frequency.

Achieved analysis of approximately 10^4 cells within minutes.

Abstract

We present a fast, high-throughput method for characterizing the motility of microorganisms in 3D based on standard imaging microscopy. Instead of tracking individual cells, we analyse the spatio-temporal fluctuations of the intensity in the sample from time-lapse images and obtain the intermediate scattering function (ISF) of the system. We demonstrate our method on two different types of microorganisms: bacteria, both smooth swimming (run only) and wild type (run and tumble) Escherichia coli, and the bi-flagellate alga Chlamydomonas reinhardtii. We validate the methodology using computer simulations and particle tracking. From the ISF, we are able to extract (i) for E. coli: the swimming speed distribution, the fraction of motile cells and the diffusivity, and (ii) for C. reinhardtii: the swimming speed distribution, the amplitude and frequency of the oscillatory dynamics. In both cases, the motility parameters are averaged over \approx 10^4 cells and obtained in a few minutes.