Roles of Sortase in Surface Expression of the Major Protein Adhesin P1, Saliva-Induced Aggregation and Adherence, and Cariogenicity of <i>Streptococcus mutans</i>
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Bibliographic record
Abstract
Sortase is a newly discovered transpeptidase that covalently links LPXTGX-containing surface proteins to the gram-positive bacterial cell wall. In this study, the sortase gene (srtA) was isolated from Streptococcus mutans NG8 by PCR. The gene encoded a 246-amino-acid protein, including a 40-amino-acid signal peptide. The srtA gene was insertionally inactivated by a tetracycline resistance cassette. P1, a major surface protein adhesin previously shown to anchor to the peptidoglycan by the LPXTGX motif, was secreted into the culture medium by the srtA mutant. In contrast, the wild-type P1 remained cell wall associated. Complementation of the mutant with srtA restored the P1 surface expression phenotype. P1 produced by the mutant, but not that produced by the wild type and the srtA-complemented mutant, was recognized by an antibody raised against the hydrophobic domain and charged tail C terminal to the LPXTGX motif. These results suggest that the failure to anchor P1 to the cell wall is due to the lack of cleavage of P1 at the LPXTGX motif. The srtA mutant was markedly less hydrophobic than the wild type and the complemented mutant. The srtA mutant failed to aggregate in the presence of saliva or salivary agglutinin and adhered poorly to saliva- or salivary agglutinin-coated hydroxylapatite. In rats, the srtA mutant colonized the teeth poorly when sucrose was absent. When sucrose was present, the srtA mutant colonized the teeth but less effectively and induced significantly less caries (P < 0.05) than the wild-type strain. In conclusion, the sortase enzyme in S. mutans is responsible for anchoring P1 to the cell surface and plays a role in modulating the surface properties and cariogenicity of S. mutans.
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Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| 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) | 0.000 | 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 it