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Monitoring Spatial Segregation in Surface Colonizing Microbial Populations
Published on: October 29, 2016
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Density-Dependent Differentiation of Bacteria in Spatially Structured Open Systems
1Department of Physics, University of Cologne, Cologne, Germany.
Biophysical Journal
|April 14, 2016
Summary
Spatial structure in open systems, like the rhizosphere, alters bacterial quorum sensing. Bacteria require 100x higher density for differentiation in microfluidic traps compared to closed systems, influenced by diffusive coupling.
Area of Science:
- Microbiology
- Systems Biology
- Chemical Engineering
Background:
- Bacterial quorum sensing is typically studied in well-mixed, closed systems.
- Natural environments, such as the rhizosphere, present bacteria with spatially structured, open systems.
- Bacteria in open systems face challenges in maintaining autoinducer concentrations for quorum sensing due to diffusion.
Purpose of the Study:
- To test if trapping bacteria in microscopic pockets of an open system triggers density-dependent differentiation.
- To investigate the role of diffusive coupling in bacterial differentiation and quorum sensing in open systems.
- To determine how spatial heterogeneity affects the minimal cell density required for bacterial differentiation.
Main Methods:
- Designed a microfluidic device with microscopic compartments to trap swimming bacteria.
- Utilized a mutant strain of Bacillus subtilis with a high differentiation rate and fluorescent reporters for competence.
- Varied the diffusive coupling of compartments to fluid flow, acting as nutrient source and autoinducer sink.
Main Results:
- The cell density required for Bacillus subtilis differentiation was 100-fold higher in microfluidic traps (open system) than in closed systems.
- Strong diffusive coupling supported early differentiation but necessitated a higher bacterial population for initiation.
- Weak diffusive coupling led to retarded bacterial growth and differentiation.
Conclusions:
- Spatial heterogeneity in open systems can promote density-dependent bacterial differentiation.
- The minimal quorum for differentiation is determined by diffusive coupling, balancing autoinducer retention and nutrient access.
- Microfluidic devices offer a platform to study bacterial behavior in ecologically relevant, spatially structured environments.
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