Possible physiological mechanisms for production of hydrogen peroxide by the ichthyotoxic flagellate Heterosigma akashiwo
Bibliographic record
Abstract
Blooms of the toxic red tide phytoplankton Heterosigma akashiwo (Raphidophyceae) are responsible for substantial losses within the aquaculture industry. The toxicological mechanisms of H.akashiwo blooms are complex and to date, heavily debated. One putative type of ichthyotoxin includes the production of reactive oxygen species (ROS) that could alter gill structure and function, resulting in asphyxiation. In this study, we investigated the potential of H.akashiwo to produce extracellular hydrogen peroxide, and have investigated which cellular processes are responsible for this production. Within all experiments, H.akashiwo produced substantial amounts of hydrogen peroxide (up to 7.6 pmol min–1 104 cells–1), resulting in extracellular concentrations of ~0.5 μmol l–1 H2O2. Measured rates of hydrogen peroxide production were directly proportional to cell density, but at higher cell densities, accuracy of H2O2 detection was reduced. Whereas light intensity did not alter H2O2 production, rates of production were stimulated when temperature was elevated. Hydrogen peroxide production was not only dependent on growth phase, but also was regulated by the availability of iron in the medium. Reduction of total iron to 1 nmol l–1 enhanced the production of H2O2 relative to iron replete conditions (10 μmol l–1 iron). From this, we collectively conclude that production of extracellular H2O2 by H.akashiwo occurs through a metabolic pathway that is not directly linked to photosynthesis.
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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 | 0.001 |
| Open science | 0.000 | 0.001 |
| Research integrity | 0.001 | 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".