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Published on: January 18, 2014
Regulatory overlap and functional redundancy among Bacillus subtilis extracytoplasmic function sigma factors
Thorsten Mascher1, Anna-Barbara Hachmann, John D Helmann
1Department of Microbiology, Wing Hall, Cornell University, Ithaca, NY 14853-8101, USA.
Journal of Bacteriology
|August 7, 2007
Summary
Bacillus subtilis ECF sigma factors are crucial for cell envelope homeostasis and antibiotic resistance. A triple mutant lacking sigM, sigW, and sigX showed impaired growth, lost multicellularity, and increased sensitivity to antibiotics.
Area of Science:
- Microbiology
- Molecular Biology
- Bacterial Genetics
Background:
- Bacillus subtilis possesses seven extracytoplasmic function (ECF) sigma factors.
- These ECF sigma factors regulate overlapping gene sets involved in cell envelope maintenance and antibiotic resistance.
Purpose of the Study:
- To investigate the physiological roles of ECF sigma factors in Bacillus subtilis.
- To identify specific ECF sigma factors critical for bacterial growth, differentiation, and stress response.
Main Methods:
- Construction of a comprehensive library of Bacillus subtilis NCIB3610 mutant strains with single, double, triple, and quadruple ECF sigma factor deletions.
- Phenotypic screening using Phenotype MicroArrays to assess motility, multicellular differentiation, and chemical sensitivity across over 200 compounds.
Main Results:
- A quadruple mutant (sigV, sigY, sigZ, ylaC) exhibited wild-type phenotypes, suggesting functional redundancy or specialized roles.
- A triple mutant (sigM, sigW, sigX) displayed biphasic growth, complete loss of multicellular differentiation (colony formation and pellicle development), and heightened sensitivity to detergents and cell wall antibiotics (beta-lactams, polymyxin B, d-cycloserine).
- Antibiotic sensitivity phenotypes in the triple mutant were often more pronounced than in strains with fewer deletions.
Conclusions:
- The ECF sigma factors SigM, SigW, and SigX play essential, non-redundant roles in Bacillus subtilis growth, multicellular development, and resistance to specific environmental stresses.
- Disruption of these key sigma factors significantly compromises bacterial cell envelope integrity and defense mechanisms.
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