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Switching and Torque Generation in Swarming E. coli
Katie M Ford1, Jyot D Antani1, Aravindh Nagarajan1
1Artie McFerrin Department of Chemical Engineering, Texas A&M University, College Station, TX, United States.
Frontiers in Microbiology
|October 4, 2018
Summary
Bacterial swarming in Escherichia coli involves flagellar motors that favor counterclockwise rotation near surfaces. This suggests altered protein dynamics aid flagellar assembly and bacterial surface motility.
Area of Science:
- Microbiology
- Bacterial Motility
- Cellular Biophysics
Background:
- Escherichia coli swarming relies on flagella for movement on semi-solid surfaces.
- Increased viscous drag near surfaces may necessitate adaptations in flagellar function.
- Flagellar switching between clockwise (CW) and counterclockwise (CCW) rotation is crucial for motility.
Purpose of the Study:
- Investigate flagellar motor behavior in swarming Escherichia coli cells.
- Determine the role of flagellar switching and protein dynamics in surface-associated motility.
- Explore mechanisms underlying flagellar assembly and export during swarming.
Main Methods:
- Measurement of flagellar motor behavior in swarmer cells.
- Analysis of flagellin gene upregulation.
- Assays on CCW-only and CW-only (FliGCW) mutants with and without surface moisture.
- Fluorescence microscopy to quantify flagella and flagellar preassemblies.
Main Results:
- Swarming cells exhibited a higher tendency for CCW motor rotation compared to planktonic cells.
- Flagellin gene upregulation was not essential for flagellar thrust or swarming.
- Surface moisture restored swarming in CCW-only mutants but not FliGCW mutants.
- FliGCW cells on agar surfaces had fewer flagella and preassemblies than planktonic cells.
Conclusions:
- Swarming Escherichia coli cells display altered flagellar motor dynamics, favoring CCW rotation.
- Surface-dependent reduction in flagella suggests impaired assembly or export in certain mutants.
- Conformational dynamics of switch proteins may be critical for flagellar complex assembly and bacterial swarming.
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