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Phenotypic and transcriptomic characterization of Bacillus subtilis mutants with grossly altered membrane composition
Letal I Salzberg1, John D Helmann
1Department of Microbiology, Cornell University, Ithaca, NY 14853-8101, USA.
Journal of Bacteriology
|September 30, 2008
Summary
Bacillus subtilis membrane lipid alterations are tolerated, but removing glycolipids increases antibiotic sensitivity and affects motility. A quadruple mutant shows viability with filament formation and altered gene expression.
Area of Science:
- Microbiology
- Molecular Biology
- Biochemistry
Background:
- The Bacillus subtilis cell membrane is composed of diacylglycerol-based lipids with diverse headgroups.
- These lipids are crucial for defining the physical and chemical properties of the lipid bilayer.
Purpose of the Study:
- To characterize the phenotypic effects of mutations affecting key membrane lipid headgroups in Bacillus subtilis.
- To investigate the impact of altered lipid composition on cell growth, antibiotic sensitivity, and gene expression.
Main Methods:
- Construction and phenotypic characterization of mutant strains lacking specific lipids: glycolipids (ugtP), phosphatidylethanolamine (pssA, psd), lysylphosphatidylglycerol (mprF), and cardiolipin (ywnE, ywjE).
- Assessment of growth proficiency, sensitivity to antimicrobial compounds, and motility.
- Transcriptome analysis of selected mutant strains.
Main Results:
- Alterations in membrane lipid headgroup composition were generally well-tolerated, with modest effects on growth.
- Mutants with reduced positively charged lipids showed increased sensitivity to cationic antimicrobials.
- Glycolipid-deficient mutants were more sensitive to sublancin and exhibited defective swarming motility.
- A quadruple mutant (ugtP pssA mprF ywnE) was viable, grew near wild-type rates, formed filaments, and displayed altered expression of SigD, FapR, sigma(M), and YvrGHb regulons.
Conclusions:
- Bacillus subtilis can tolerate significant changes in membrane lipid headgroup composition.
- Specific lipids play roles in antibiotic resistance and cell surface properties.
- Altered lipid profiles trigger significant changes in gene expression, including stress responses.
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