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Motile bacteria in a critical fluid mixture
Nick Koumakis1, Clémence Devailly1, Wilson C K Poon1
1SUPA and School of Physics & Astronomy, The University of Edinburgh, James Clerk Maxwell Building, Peter Guthrie Tait Road, Edinburgh EH9 3FD, Scotland, United Kingdom.
Physical Review. E
|July 18, 2018
Summary
We observed Escherichia coli bacteria swimming near a critical point, creating visible trails. These trails result from local phase changes, not shear forces, and can reveal fluid dynamics.
Area of Science:
- Soft Matter Physics
- Microbiology
- Physical Chemistry
Background:
- Bacteria swimming behavior is influenced by their surrounding fluid environment.
- Critical points in solutions exhibit unique physical properties and fluctuations.
- Previous studies noted bacterial trails in liquid crystals due to shear.
Purpose of the Study:
- To investigate the swimming dynamics of Escherichia coli near a critical point.
- To identify the mechanism behind transient trails produced by swimming bacteria.
- To utilize these trails as a probe for critical fluid phenomena.
Main Methods:
- Phase-contrast microscopy to visualize bacterial swimming and trails.
- Quantitative image analysis of bacterial trails.
- Computational simulations to model trail formation.
- Experiments conducted in a nonionic surfactant (C_{12}E_{5}) solution near its critical point.
Main Results:
- Swimming Escherichia coli bacteria generate transient, visible trails.
- Trails are caused by local phase reorganization due to differential adsorption.
- This mechanism differs from shear-induced trails observed in liquid crystals.
Conclusions:
- Bacterial swimming can induce measurable changes in critical fluid phases.
- The observed trails provide a novel method to study critical fluid dynamics.
- Differential adsorption is the key mechanism for trail formation in this system.
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