Experimental evidence for plasmid-borne<i>nor-nir</i>genes in<i>Sinorhizobium meliloti</i>JJ1c10
Bibliographic record
Abstract
In denitrification, nir and nor genes are respectively required for the sequential dissimilatory reduction of nitrite and nitric oxide to form nitrous oxide. Their location on the pSymA megaplasmid of Sinorhizobium meliloti was confirmed by Southern hybridization of its clones with specific structural gene probes for nirK and norCB. A 20-kb region of pSymA containing the nor-nir genes was delineated by nucleotide sequence analysis. These genes were linked to the nap genes encoding periplasmic proteins involved in nitrate reduction. The nor-nir-nap segment is situated within 30 kb downstream from the nos genes encoding nitrous oxide reduction, with a fix cluster intervening between nir and nos. Most of these predicted nor-nir and accessory gene products are highly homologous with those of related proteobacterial denitrifiers. Functional tests of Tn5 mutants confirmed the requirement of the nirV product and 1 unidentified protein for nitrite reduction as well as the norB-D products and another unidentified protein for nitric oxide reduction. Overall comparative analysis of the derived amino acid sequences of the S. meliloti gene products suggested a close relationship between this symbiotic N2 fixer and the free-living non-N2-fixing denitrifier Pseudomonas G-179, despite differences in their genetic organization. This relationship may be due to lateral gene transfer of denitrification genes from a common donor followed by rearrangement and recombination of these genes.
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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".