Steroid catabolism in bacteria: Genetic and functional analyses of stdH and stdJ in Pseudomonas putida DOC21
Bibliographic record
Abstract
Pseudomonas putida DOC21 assimilates a large variety of steroids, including bile acids, via a single 9, 10-seco pathway. Two specific mutants knocked down in stdH and stdJ were obtained by deletion (strains P. putida DOC21ΔstdH and P. putida DOC21ΔstdJ). Analysis of these mutants revealed that both had lost the ability to fully degrade bile acids and that the genes stdH and stdJ are involved in oxidation of the A and B rings of the polycyclic steroid structure. Moreover, whereas P. putida DOC21ΔstdH and P. putida DOC21ΔstdJ were unable to degrade testosterone or 4-androstene-3,17-dione (AD), P. putida DOC21ΔstdJ was also unable to assimilate androsta-1,4-diene-3,17-dione (ADD). When cultured in medium containing lithocholate and succinate, P. putida DOC21ΔstdH and P. putida DOC21ΔstdJ accumulated AD and ADD, respectively. Genetic and bioinformatics analyses revealed that: (i) stdH encodes a 3-ketosteroid-Δ1-dehydrogenase; (ii) StdJ is the reductase component of a 3-ketosteroid 9α-hydroxylase; (iii) the trans-expression of stdH and stdJ in the corresponding mutant restored the lost catabolic function(s), and (iv) full steroid metabolism by P. putida DOC21ΔstdH was restored by its expression of kstD2, but not kstD1 or kstD3, of Rhodococcus ruber Chol-4. Our results shed light on the systems used by bacteria to oxidize the A and B rings of steroid compounds. In addition, as the mutants described herein were able to synthesize two pharmaceutically important synthons, AD and ADD, they may be of value in industrial applications.
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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 | 0.001 |
| Bibliometrics | 0.000 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.001 |
| 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".