To cross or not to cross: Collective swimming of Escherichia coli under two-dimensional confinement

Dipanjan Ghosh, Xiang Cheng

Research output: Contribution to journalArticlepeer-review

Abstract

Bacteria suspended in fluids swim collectively and display fascinating emergent dynamics. Although bacterial collective swimming in bulk suspensions has been well studied, its counterpart in confined two-dimensional (2D) geometries relevant to many natural habitats of bacteria is still poorly understood. Here, through carefully designed experiments on Escherichia coli in a Hele-Shaw geometry, we show that a small change in the degree of confinement leads to a drastic change in bacterial collective swimming. While a long-range nematic order emerges for bacteria that can cross over each other during encounters, a slight decrease of the confining height that prevents the crossing leads to the formation of bacterial clusters with a short-range polar order. By tracking the swimming kinetics of individual bacteria, we reveal the microscopic origins of the two emergent collective phases and illustrate the effect of the collective dynamics on the swimming behaviors of single bacteria. Our study provides insights into bacterial collective swimming under confinement and demonstrates a simple way to control the emergent symmetry of collective phases.

Original languageEnglish (US)
Article number023105
JournalPhysical Review Research
Volume4
Issue number2
DOIs
StatePublished - Jun 2022

Bibliographical note

Funding Information:
We are indebted to Shuo Guo for helping with the experiments and for providing valuable insights. We also thank Renan Gross and Oliver Meacock for helping with the code used for segmenting and tracking bacteria in 2D, and thank Robert Großmann, Shashank Kamdar, Zhengyang Liu, Yi Peng, Fernando Peruani and Xinliang Xu for helpful discussions. This work was funded by NSF CBET Grants No. 1702352 and No. 2028652 and the David and Lucile Packard Foundation. We dedicate this paper to the memory of our mentor and friend, Prof. James W. Swan.

Publisher Copyright:
© 2022 authors.

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