Regulation of the induction of bicarbonate uptake by dissolved CO<sub>2</sub> in the marine diatom, <i>Phaeodactylum tricornutum</i>
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Bibliographic record
Abstract
ABSTRACT Physiological properties of photosynthesis were determined in the marine diatom, Phaeodactylum tricornutum UTEX640, during acclimation from 5% CO 2 to air and related to H 2 CO 3 dissociation kinetics and equilibria in artificial seawater. The concentration of dissolved inorganic carbon at half maximum rate of photosynthesis ( K 0·5 [DIC]) value in high CO 2 ‐grown cells was 1009 mmol m − 3 but was reduced three‐fold by the addition of bovine carbonic anhydrase (CA), whereas in air‐grown cells K 0·5 [DIC] was 71 mmol m − 3 , irrespective of the presence of CA. The maximum rate of photosynthesis ( P max ) values varied between 300 and 500 μ mol O 2 mg Chl − 1 h − 1 regardless of growth p CO 2 . Bicarbonate dehydration kinetics in artificial seawater were re‐examined to evaluate the direct HCO 3 − uptake as a substrate for photosynthesis. The uncatalysed CO 2 formation rate in artificial seawater of 31·65°/ oo of salinity at pH 8·2 and 25 °C was found to be 0·6 mmol m − 3 min − 1 at 100 mmol m − 3 DIC, which is 53·5 and 7·3 times slower than the rates of photosynthesis exhibited in air‐ and high CO 2 ‐grown cells, respectively. These data indicate that even high CO 2 ‐grown cells of P. tricornutum can take up both CO 2 and HCO 3 − as substrates for photosynthesis and HCO 3 − use improves dramatically when the cells are grown in air. Detailed time courses were obtained of changes in affinity for DIC during the acclimation of high CO 2 ‐grown cells to air. The development of high‐affinity photosynthesis started after a 2–5 h lag period, followed by a steady increase over the next 15 h. This acclimation time course is the slowest to be described so far. High CO 2 ‐grown cells were transferred to controlled DIC conditions, at which the concentrations of each DIC species could be defined, and were allowed to acclimate for more than 36 h. The K 0·5 [DIC] values in acclimated cells appeared to be correlated only with [CO 2(aq) ] in the medium but not to HCO 3 − , CO 3 2 − , total [DIC] or the pH of the medium and indicate that the critical signal regulating the affinity of cells for DIC in the marine diatom, P. tricornutum , is [CO 2(aq) ] in the medium.
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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