Pseudo-nitzschia sp. cf. pseudodelicatissima - a confirmed producer of domoic acid from the northern Gulf of Mexico
Bibliographic record
Abstract
Domoic acid (DA), a potent neurotoxin, is synthesized by certain members of the ubiquitous marine diatom genus Pseudo-nitzschia. We recently detected elevated concentrations of DA in phytoplankton field samples from the northern Gulf of Mexico. In searching for a possible source of the toxin, we used a receptor-binding assay to detect DA activity in cultures of P. sp. cf. pseudodelicatissima (Hasle) isolated from this region and confirmed its presence in 2 of 7 clones using liquid chromatography coupled with tandem mass-spectrometric detection (LC-MS/MS). Unlike other toxic Pseudo-nitzschia species examined previously (e.g., P. multiseries, P. australis), cellular levels and net production of DA in these clones were highest in the early exponential phase, while the population growth rate was high and cell concentration was low. There was a negative correlation between cellular DA and cell concentration. The maximum cellular DA activity in cultures was 36 fg DA equiv. cell -1 . No net toxin production was evident in the stationary phase, yet extracellular DA levels increased markedly during this period to as much as 88% of the total DA in the cultures. Interestingly, these 2 toxic clones were able to enlarge their cell size after the apical axes declined to 15 to 25 m, and these larger cells had considerably higher levels of DA than the original small cells. This study unequivocally establishes P. sp. cf. pseudodelicatissima as a source of DA in the northern Gulf of Mexico. Moreover, our work suggests that rapidly growing, rather than nutrient-limited, populations of this diatom should yield maximum net DA production rates and DA cell quotas. Thus, the presence of P. sp. cf. pseudodelicatissima cells, even at the low levels of early, rapidly growing bloom stages, can potentially lead to toxic events.
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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".