Regulation of tryptophan synthase gene expression in <i>Chlamydia trachomatis</i>
Bibliographic record
Abstract
We previously reported that Chlamydia trachomatis expresses the genes encoding tryptophan synthase (trpA and trpB). The results presented here indicate that C. trachomatis also expresses the tryptophan repressor gene (trpR). The complement of genes regulated by tryptophan levels in C. trachomatis is limited to trpBA and trpR. trp gene expression was repressed if chlamydiae-infected HeLa cells were cultured the presence of tryptophan and induced if grown in tryptophan-depleted medium or in the presence of IFN-gamma. Furthermore, expression of the trp genes in strains which encode a functional tryptophan synthase is repressed when infected cells are cultured in the presence of the tryptophan precursor indole. Results from experiments with cycloheximide, an inhibitor of eukaryotic protein synthesis, indicate that in addition to the absolute size of the intracellular tryptophan pool, host competition for available tryptophan plays a key role in regulating expression of the trp genes. The tryptophan analogue, 5-fluorotryptophan, repressed trp gene expression and induced the formation of aberrant organisms of C. trachomatis. The growth-inhibitory properties of 5-fluorotryptophan could be reversed with exogenous tryptophan but not indole. In total, our results indicate that the ability to regulate trp gene expression in response to tryptophan availability is advantageous for the intracellular survival of this organism. Furthermore, the fact that C. trachomatis has retained the capacity to respond to tryptophan limitation supports the view that the in vivo antichlamydial effect of IFN-gamma is via the induction of the tryptophan-degrading enzyme, indoleamine 2,3-dioxygenase.
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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".