<i>pcd</i> Mutants of <i>Streptomyces clavuligerus</i> Still Produce Cephamycin C
Bibliographic record
Abstract
Biosynthesis of cephamycin C in Streptomyces clavuligerus involves the initial conversion of lysine to alpha-aminoadipic acid. Lysine-6-aminotransferase and piperideine-6-carboxylate dehydrogenase carry out this two-step reaction, and genes encoding each of these enzymes are found within the cephamycin C gene cluster. However, while mutation of the lat gene causes complete loss of cephamycin production, pcd mutants still produce cephamycin at 30% to 70% of wild-type levels. Cephamycin production by pcd mutants could be restored to wild-type levels either by supplementation of the growth medium with alpha-aminoadipic acid or by complementation of the mutation with an intact copy of the pcd gene. Neither heterologous PCR nor Southern analyses showed any evidence for the presence of a second pcd gene. Furthermore, cell extracts from pcd mutants lack detectable PCD activity. Cephamycin production in the absence of detectable PCD activity suggests that S. clavuligerus must have some alternate means of producing the aminoadipyl-cysteinyl-valine needed for cephamycin biosynthesis.
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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) | 0.001 | 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 | 0.001 |
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".