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A σW-dependent stress response in Bacillus subtilis that reduces membrane fluidity
Anthony W Kingston1, Chitra Subramanian, Charles O Rock
1Department of Microbiology, Cornell University, Ithaca, NY 14853-8101, USA.
Molecular Microbiology
|May 6, 2011
Summary
Bacillus subtilis uses the sigma W (σW) stress response to adjust membrane fluidity. This mechanism alters fatty acid synthesis enzymes, reducing fluidity to protect against cell envelope stresses like detergents.
Area of Science:
- Microbiology
- Bacterial Physiology
- Stress Response Mechanisms
Background:
- Bacteria possess a cell envelope stress response to maintain cell integrity under physical and chemical stress.
- Homeoviscous adaptation allows cells to regulate membrane biophysical properties by altering fatty acid composition.
- The extracytoplasmic function sigma factor σ(W) is involved in bacterial stress responses.
Purpose of the Study:
- To identify a homeoviscous adaptation mechanism in Bacillus subtilis regulated by σ(W).
- To elucidate the role of σ(W) in modulating membrane fluidity in response to cell envelope stress.
Main Methods:
- Investigated the regulation of the fabHa-fabF operon by σ(W) using promoter activity assays.
- Analyzed changes in fatty acid biosynthesis enzyme levels (FabHa, FabF) and fatty acid composition.
- Assessed bacterial sensitivity to detergents and antimicrobial compounds following genetic manipulation.
Main Results:
- Detergents activate a σ(W)-dependent promoter in the fabHa-fabF operon.
- Activation leads to decreased FabHa and increased FabF, resulting in shorter straight-chain fatty acids and longer average chain lengths, reducing membrane fluidity.
- Inactivation of the σ(W)-dependent promoter increased sensitivity to detergents and antimicrobials.
Conclusions:
- The σ(W) stress response in Bacillus subtilis regulates homeoviscous adaptation by opposing the expression of FabHa and FabF.
- This mechanism conditionally decreases membrane fluidity, enhancing resistance to cell envelope-targeting compounds.
- σ(W) plays a crucial role in bacterial survival under specific environmental stresses.
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