The alarmone (p)ppGpp is part of the heat shock response of <i>Bacillus subtilis</i>
Bibliographic record
Abstract
Abstract Here, B. subtilis was used as a model organism to investigate how cells respond and adapt to proteotoxic stress conditions. Our experiments suggested that the stringent response, caused by raised levels of the (p)ppGpp alarmone, plays a role during thermotolerance development and the heat shock response. Accordingly, our experiments revealed a rapid increase of cellular (p)ppGpp levels upon heat shock as well as salt- and oxidative stress. Strains lacking (p)ppGpp exhibited increased stress sensitivity, while raised (p)ppGpp levels conferred increased stress tolerance to heat- and oxidative stress. During thermotolerance development, stress response genes were highly up-regulated together with a concurrent transcriptional down-regulation of the rRNA, which was influenced by the second messenger (p)ppGpp and the transcription factor Spx. Remarkably, we observed that (p)ppGpp appeared to control the cellular translational capacity and that during heat stress the raised cellular levels of the alarmone were able to curb the rate of protein synthesis. Furthermore, (p)ppGpp controls the heat-induced expression of Hpf and thus the formation of translationally inactive 100S disomes. These results indicate that B. subtilis cells respond to heat-mediated protein unfolding and aggregation, not only by raising the cellular repair capacity, but also by decreasing translation involving (p)ppGpp mediated stringent response to concurrently reduce the protein load for the cellular protein quality control system. Author Summary Here we demonstrate that the bacterial stringent response, which is known to slow down translation upon sensing nutrient starvation, is also intricately involved in the stress response of B. subtilis cells. The second messengers (p)ppGpp act as pleiotropic regulators during the adaptation to heat stress. (p)ppGpp slows down translation and is also involved in the transcriptional down-regulation of the translation machinery, together with the transcriptional stress regulator Spx. The stress-induced elevation of cellular (p)ppGpp levels confers increased stress tolerance and facilitates an improved protein homeostasis by reducing the load on the protein quality control system.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".