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Novel modulators controlling entry into sporulation in Bacillus subtilis.
Sharon Garti-Levi1, Ashlee Eswara, Yoav Smith
1Department of Microbiology and Molecular Genetics, Institute for Medical Research Israel-Canada (IMRIC), The Hebrew University-Hadassah Medical School, The Hebrew University of Jerusalem, Jerusalem, Israel.
Journal of Bacteriology
|January 22, 2013
Summary
Bacillus subtilis uses SivA, SivB, and SivC to prevent premature sporulation. These factors, activated by Spo0A, inhibit the sporulation phosphorelay, ensuring sporulation only occurs during nutrient deprivation.
Area of Science:
- Microbiology
- Molecular Biology
- Bacterial Development
Background:
- Bacillus subtilis sporulation is a complex developmental process triggered by nutrient deprivation.
- Environmental signals activate a phosphorelay system, leading to the phosphorylation of Spo0A, a master transcriptional regulator.
- Spo0A controls the expression of genes essential for initiating sporulation.
Purpose of the Study:
- To identify genes regulated by Spo0A during exponential growth.
- To investigate the function of newly identified genes in the regulation of sporulation initiation.
- To elucidate the mechanism by which Bacillus subtilis prevents premature sporulation.
Main Methods:
- Transcriptional analysis to identify Spo0A-controlled genes during exponential growth.
- Gene knockout and overexpression studies to assess the role of identified genes.
- Biochemical assays to measure Spo0A phosphorylation levels and kinase activity.
Main Results:
- Three genes, sivA, sivB (bslA), and sivC, were found to be upregulated by Spo0A during exponential growth.
- SivA, SivB, and SivC proteins were identified as inhibitors of Spo0A activation.
- The Siv factors reduce the activity of histidine kinases in the sporulation phosphorelay, decreasing Spo0A phosphorylation.
Conclusions:
- Spo0A positively regulates genes encoding inhibitors of its own activation, creating a negative feedback loop.
- These Siv factors act as modulators to prevent inappropriate entry into sporulation when nutrients are abundant.
- This regulatory mechanism ensures efficient resource allocation and timely initiation of sporulation in Bacillus subtilis.
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