Regulation of d-alanylation of lipoteichoic acid in Streptococcus gordonii
Bibliographic record
Abstract
d-Alanyl esters on lipoteichoic acid (LTA) are involved in adhesion, biofilm formation, resistance to cationic antimicrobial peptides, and immune stimulation. There is evidence that bacteria can modulate the level of d-alanyl esters on LTA in response to challenge, but the mechanism of regulation appears to be different among bacteria. In this study, expression of the dlt operon responsible for d-alanylation of LTA was examined in the commensal bacterium Streptococcus gordonii. dlt expression was assessed using the dlt promoter-lacZ reporter gene assay, LTA d-alanine content measurements and dlt mRNA quantification. The results showed that dlt expression was growth phase-dependent, with the greatest expression at the mid-exponential phase of growth. In contrast to Staphylococcus aureus, dlt expression in Strep. gordonii was not affected by the exogenous addition of Mg(2+) or K(+). Interestingly, dlt expression was upregulated under acidic conditions or when cells were stressed with polymyxin B, indicating that cell envelope stress may be a signal for dlt expression. In view of these results, mutants defective in the cell envelope stress LiaSR two-component regulatory system were constructed. The liaS and liaR mutants showed an increase in dlt expression over the parent strain at neutral pH. The mutants failed to respond to low pH and polymyxin B stress; dlt expression remained the same in the presence or absence of these stresses. These results suggest that dlt expression in Strep. gordonii is regulated by the LiaSR regulatory system in response to environmental signals such as pH and polymyxin B. The regulation appears to be complex, involving both repression and activation mechanisms.
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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 | 0.000 | 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 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".