Streptococcal viability and diminished stress tolerance in mutants lacking the signal recognition particle pathway or YidC2
Bibliographic record
Abstract
The signal recognition particle (SRP)-translocation pathway is conserved in all three domains of life and delivers membrane and secretory proteins to the cytoplasmic membrane or endoplasmic reticulum. We determined the requirement in the cariogenic oral pathogen Streptocococcus mutans of the three universally conserved elements of the SRP pathway: Ffh/SRP54, scRNA, and FtsY/SRalpha. Previously, we reported that insertional interruption of S. mutans ffh was not lethal, but resulted in acid sensitivity. To test whether S. mutans could survive extensive disruption of the SRP pathway, single and double deletions of genes encoding Ffh, scRNA, and FtsY were generated. Without environmental stressors, all mutant strains were viable, but unlike the wild-type, none could initiate growth at pH 5.0 or in 3.5% NaCl. Survival of challenge with 0.3 mM H(2)O(2) was also diminished without ffh. Members of the YidC/Oxa1/Alb3 family are also ubiquitous, involved in the translocation and assembly of membrane proteins, and have been identified in prokaryotes/mitochondria/chloroplasts. Two genes encoding YidC homologs, YidC1 and YidC2, are present in streptococcal genomes with both expressed in S. mutans. Deletion of YidC1 demonstrated no obvious phenotype. Elimination of YidC2 resulted in a stress-sensitive phenotype similar to SRP pathway mutants. Mutants lacking both YidC2 and SRP components were severely impaired and barely able to grow, even in the absence of environmental stress. Here, we report the dispensability of the cotranslational SRP protein translocation system in a bacterium. In S. mutans, this pathway contributes to protection against rapid environmental challenge and may overlap functionally with YidC2.
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How this classification was reachedexpand
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 | 0.001 | 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 | 0.001 |
| 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 teacher head, 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".