Nitrogen‐fixation strategies and Fe requirements in cyanobacteria
Why this work is in the frame
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Bibliographic record
Abstract
Diazotrophic (nitrogen‐fixing) cyanobacteria are important contributors of new nitrogen to oligotrophic environments and greatly influence oceanic productivity. We investigated how iron availability influences the physiology of cyanobacterial diazotrophs with different strategies for segregating nitrogen fixation and photosynthesis. We examined growth, photosynthesis, nitrogen fixation, and Fe requirements of the filamentous nonheterocystous Trichodesmium , the filamentous heterocystous Anabaena , and the unicellular Cyanothece under a range of Fe concentrations. Under similar Fe concentrations the three species differed in N 2 ‐fixation rates, photosynthetic activity, the relative abundance of the photosynthetic units PSI : PSII, elemental stoichiometry, and Fe use efficiency. Complex colonial forms such as Trichodesmium and Anabaena are more likely to be Fe limited in their natural environments and are more efficient at utilizing Fe than unicellular diazotrophs such as Cyanothece . The varied physiological responses to Fe availability of the three cyanobacteria reflect their nitrogen fixation strategies, cell size, unicellular or colonial organization, and may explain, at least in part, the ecological distribution of these photosynthetic bacteria.
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Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| 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 it