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Updated: Sep 11, 2025
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Using Microtiter Dish Radiolabeling for Multiple In Vivo Measurements Of Escherichia coli pppGpp Followed by Thin Layer Chromatography
Published on: June 4, 2019
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(p)ppGpp-dependent activation of gene expression during nutrient limitation
Sathya Narayanan Nagarajan1, Adam Rosenthal2, Jonathan Dworkin1
1Department of Microbiology and Immunology, Vagelos College of Physicians and Surgeons, Columbia University, New York, New York, USA.
Mbio
|August 18, 2025
Summary
Bacteria adapt to nutrient scarcity by reducing energy use and activating survival genes. This study reveals how guanosine tetra- and penta-phosphate ((p)ppGpp) links reduced protein synthesis to activating survival genes like hpf in Bacillus subtilis.
Area of Science:
- Bacterial Physiology
- Molecular Biology
- Gene Regulation
Background:
- Bacteria entering nutrient limitation slow growth and remodel metabolism to conserve energy.
- This adaptation involves decreased transcription of energy-intensive genes and increased expression of survival genes.
- Guano sine tetra- and penta-phosphate ((p)ppGpp) are key mediators of this metabolic shift, particularly affecting protein synthesis.
Purpose of the Study:
- To elucidate the molecular mechanism linking nutrient limitation, reduced protein synthesis, and the activation of specific survival genes in Bacillus subtilis.
- To investigate the role of (p)ppGpp in the transcriptional regulation of the hpf gene, which protects ribosomes during nutrient stress.
- To understand how this regulatory network facilitates bacterial adaptation and developmental processes like sporulation and competence.
Main Methods:
- Analysis of gene transcription under nutrient-limiting conditions in Bacillus subtilis.
- Investigated the role of the alternative sigma factor sigma-H (σH) and its regulator AbrB in hpf gene expression.
- Assessed the necessity of (p)ppGpp for activating genes involved in sporulation and genetic competence.
Main Results:
- Demonstrated that (p)ppGpp is crucial for activating the hpf gene during the exit from rapid growth in nutrient-limited Bacillus subtilis.
- Showed that hpf transcription requires σH, whose expression is derepressed when (p)ppGpp reduces global protein synthesis, lowering AbrB levels.
- Confirmed that (p)ppGpp is essential for the expression of genes mediating bacterial developmental fates, including sporulation and competence.
Conclusions:
- A novel regulatory mechanism couples reduced global protein synthesis, mediated by (p)ppGpp, to the transcriptional activation of survival genes like hpf.
- This pathway links translational regulation (protein synthesis) with transcriptional regulation (gene expression) during nutrient stress.
- The identified mechanism is vital for bacterial adaptation to nutrient limitation and the successful execution of developmental programs.
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