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Analysis of the relationship between the decrease in pH and accumulation of 3-phosphoglyceric acid in developing
N G Magill1, A E Cowan, M A Leyva-Vazquez
1Department of Biochemistry, University of Connecticut Health Center, Farmington 06030, USA.
Journal of Bacteriology
|April 1, 1996
Summary
Forespore pH decrease in Bacillus subtilis is linked to 3-phosphoglyceric acid (3PGA) accumulation, requiring sigma G-dependent transcription. This pH change inhibits phosphoglycerate mutase, leading to 3PGA buildup, but large 3PGA depots are not essential for sporulation.
Area of Science:
- Microbiology
- Cell Biology
- Biochemistry
Background:
- Bacterial sporulation involves complex intracellular changes.
- Forespore development in Bacillus species is critical for spore formation.
- Previous studies suggested a link between forespore pH and metabolite accumulation.
Purpose of the Study:
- To investigate the relationship between forespore pH decrease and 3-phosphoglyceric acid (3PGA) accumulation during Bacillus subtilis sporulation.
- To determine the transcriptional regulation and enzymatic basis for forespore pH changes and 3PGA accumulation.
- To assess the necessity of 3PGA accumulation for successful spore germination and outgrowth.
Main Methods:
- Analysis of pH and 3PGA levels in sporulating Bacillus subtilis cells and mutants.
- Investigating the role of sigma G and sigma K transcription factors in forespore pH regulation.
- Enzymatic assays and genetic manipulation of phosphoglycerate mutase (PGM) levels in B. subtilis.
- Monitoring spore germination and outgrowth in strains with altered 3PGA levels.
Main Results:
- A pH decrease of 1-1.2 units in the forespore precedes 3PGA accumulation.
- Sigma G-dependent forespore transcription, but not sigma K-dependent mother cell transcription, is required for the forespore pH decrease.
- A strong correlation exists between forespore pH decrease and 3PGA accumulation, mediated by decreased phosphoglycerate mutase activity.
- Elevating forespore pH or increasing PGM levels reduces 3PGA accumulation.
- High PGM levels do not impede sporulation, germination, or outgrowth.
Conclusions:
- The forespore pH decrease is a critical regulatory event during Bacillus subtilis sporulation, dependent on sigma G.
- This pH drop inhibits phosphoglycerate mutase, leading to the accumulation of 3PGA.
- Significant accumulation of 3PGA within the forespore is not essential for the completion of the sporulation cycle or spore viability.