A Two-Component <i>covRS</i> Regulatory System Regulates Expression of Fructosyltransferase and a Novel Extracellular Carbohydrate in <i>Streptococcus mutans</i>
Bibliographic record
Abstract
The expression of fructosyltransferase (FTF), the enzyme that synthesizes fructan from sucrose, is regulated in the cariogenic bacterium Streptococcus mutans. However, the exact mechanism of FTF regulation is unknown. In this study, the role of a two-component regulatory system (covRS) in FTF expression was investigated. A CovR-defective mutant of S. mutans NG8 was constructed by homologous recombination. By use of immunoblotting, the mutant was shown to overexpress FTF in the absence of sucrose, while the wild type and a covRS-complemented mutant showed sucrose-inducible FTF expression. Reverse transcription-PCR showed that the ftf transcript levels were increased in the covR mutant, suggesting regulation at the transcriptional level. The covR mutant was also found to overproduce extracellular carbohydrate, and this phenotype was reversed by covRS complementation. Paper chromatographic studies and chemical tests showed that the extracellular carbohydrate contained glucose and glucuronic acid but not fructose. These results suggest that the extracellular carbohydrate was not fructan. The production of a glucose- and glucuronic acid-containing extracellular carbohydrate has not been reported for S. mutans and may be considered novel. In conclusion, the results indicate that the expression of FTF and a glucose- and glucuronic acid-containing carbohydrate was negatively regulated by the covRS two-component regulatory system in S. mutans.
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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) | 0.001 | 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) | 0.000 | 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".