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Published on: May 28, 2007
Microbubbles reveal chiral fluid flows in bacterial swarms
Yilin Wu1, Basarab G Hosu, Howard C Berg
1Rowland Institute at Harvard and Department of Molecular and Cellular Biology, Harvard University, Cambridge, MA 02138, USA.
Summary
Microbubbles reveal a fast-flowing fluid river at the edge of bacterial swarms. This discovery enhances understanding of bacterial colony expansion and communication dynamics.
Area of Science:
- Microbiology
- Fluid Dynamics
- Biophysics
Background:
- Bacterial swarming is a collective colony expansion mechanism.
- Understanding fluid dynamics is crucial for bacterial motility and communication.
- Previous methods for tracking swarm fluid motion were limited.
Purpose of the Study:
- To investigate the fluid dynamics of bacterial swarming.
- To identify novel methods for visualizing fluid flow during swarming.
- To elucidate the mechanisms driving fluid transport at the swarm edge.
Main Methods:
- Utilized micrometer-sized bubbles as tracers for fluid motion.
- Generated microbubbles by introducing a water-insoluble surfactant (Span 83) onto agar surfaces.
- Observed fluid flow using microscopy and analyzed bacterial flagellar action.
Main Results:
- Discovered a significant clockwise-flowing fluid stream ('river') at the leading edge of Escherichia coli swarms.
- Measured fluid flow speeds approximately three times faster than the swarm expansion rate (around 10 μm/s).
- Correlated fluid flow patterns with the rotational action of bacterial flagella.
Conclusions:
- Bacterial flagellar rotation generates directed fluid flow crucial for swarming.
- The observed fluid 'river' facilitates long-range transport of molecules, such as secretory vesicles.
- Findings offer insights into bacterial collective behavior and potential applications in microfluidic device engineering.
