Targets for hydrogen-peroxide-induced damage to suspension and biofilm cells of Streptococcus mutans
Bibliographic record
Abstract
Hydrogen peroxide (H2O2) is considered a major endogenous source of oxidative stress to oral bacteria and also is widely used in oral care products. Our study objectives were to identify specific targets for H2O2-induced damage to cells of Streptococcus mutans in suspensions and monospecies biofilms and to differentiate bacteriostatic and bactericidal actions of the peroxide. Streptococcus mutans was grown in suspension cultures and fed-batch biofilms for assessing relative sensitivities of viability, glycolysis, and protein synthesis to H2O2 damage. Biofilm cells were found to have essentially the same peroxide sensitivity as cells in suspensions. H2O2 at low concentrations of about 16.3 mmol/L was highly inhibitory for glycolysis and mainly bacteriostatic. The most sensitive target detected for glycolytic inhibition was glyceraldehyde-3-phosphate dehydrogenase with IC50 (50% inhibitory concentration) values of ca. 2.2 mmol/L for suspension cells and 2.3 mmol/L for biofilms with 15 min treatments. The phosphoenolpyruvate:glucose phosphotransferase pathway was less sensitive with an IC50 of ca. 10 mmol/L. Aldolase was not inhibited at bacteriostatic concentrations of the peroxide. For suspensions and biofilms, acidification somewhat diminished peroxide sensitivity, while increased temperature enhanced sensitivity. At concentrations above about 30 mmol/L, H2O2 became mainly bactericidal but not mutagenic for S. mutans. A major target for bactericidal damage was protein synthesis, thus rendering cells incapable of repairing or replacing oxidatively damaged proteins.
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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".