Involvement of reductases <scp>I</scp>ru<scp>O</scp> and <scp>N</scp>tr<scp>A</scp> in iron acquisition by <scp><i>S</i></scp><i>taphylococcus aureus</i>
Bibliographic record
Abstract
To obtain host iron, Staphylococcus aureus secretes siderophores staphyloferrin A (SA) or staphyloferrin B (SB), and accesses heme iron through use of iron-regulated surface determinant proteins. While iron transport in S. aureus is well documented, there is scant information about proteins required to access iron from complexes in the cytoplasm. In vitro studies identified a pyridine nucleotide-disulfide oxidoreductase, named IruO, as an electron donor for the heme monooxygenases IsdG and IsdI, promoting heme degradation. Here, we show that an iruO mutant was not debilitated for growth on heme, suggesting involvement of another reductase. NtrA is an iron-regulated nitroreductase and, as with the iruO mutant, a ntrA mutant grew on heme comparable with wild type (WT). In contrast, a iruO ntrA double mutant was severely debilitated for growth on heme, a phenotype that was complemented by expression of either iruO or ntrA in trans, demonstrating their overlapping role in heme-iron utilization. Contrasting the involvement of multiple reductases for heme iron utilization, ntrA was shown essential for iron utilization using SA, although not SB or other siderophores tested, and an iruO mutant was incapable of deferoxamine-mediated growth. Accordingly, virulence of WT S. aureus, but not an iruO mutant, was enhanced in mice receiving deferoxamine.
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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) | 0.000 | 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 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".