Regulation of <i>Sinorhizobium meliloti</i> 1021 <i>rrnA</i>-reporter gene fusions in response to cold shock
Bibliographic record
Abstract
We previously reported that mutants of Sinorhizobium meliloti 1021 carrying luxAB insertions in each of the three 16S rRNA genes exhibited a dramatic (> or = 28-fold) increase in luminescence following a temperature downshift from 30 to 15 degrees C. These results raised the possibility that the rRNA operons (rrn) of S. meliloti were cold shock loci. In testing this possibility, we found that fusion of the S. meliloti 1021 rrnA promoter to two different reporter genes, luxAB and uidA, resulted in hybrid genes that were transiently upregulated (as measured by transcript accumulation) about four- to sixfold in response to a temperature downshift. These results are consistent with the hypothesis that the rrn promoters are transiently upregulated in response to cold shock. However, much of the apparent cold shock regulation of the initial luxAB insertions was due to an unexpected mechanism: an apparent temperature-dependent inhibition of translation. Specifically, the rrnA sequences from +1 to +172 (relative to the start of transcription) were found to greatly decrease the ability of S. meliloti to translate hybrid rrn-luxAB transcripts into active protein at 30 degrees C. This effect, however, was largely eliminated at 15 degrees C. Possible mechanisms for the apparent transient increase in rrnA promoter activity and temperature-dependent inhibition of translation are discussed.
Fetched live from OpenAlex and de-inverted. Abstracts are not stored in this database: the inverted indexes are 8.6 GB of the frame’s 9.3 GB of text, and the host has 13 GB free.
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) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 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 | 0.001 |
| Insufficient payload (model declined to judge) | 0.001 | 0.001 |
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".