Proteomics of Desulfovibrio desulfuricans and X-ray absorption spectroscopy to investigate mercury methylation in the presence of selenium
Bibliographic record
Abstract
The effects of mercury added as Hg(2+) and selenium as selenite to cultures of the sulfate reducing bacterium Desulfovibrio desulfuricans were investigated under controlled laboratory conditions. There was no significant difference in the growth curves in comparison to control except in the 0.5 μM Hg-6.3 μM Se combined system in which Hg methylation was significantly reduced. A significant decrease in the production of methylmercury indicates a disruption of the methylation process due to the presence of the relatively high concentrations of Se in the system, suggesting a modification of the biological pathway. The results of detailed 2D gel electrophoresis in combination with mass spectrometry confirmed that the Hg methylation process should certainly be influenced when the protein Dde_1198 protein-glutamate O-methyltransferase was totally suppressed in a culture containing 0.5 μM Hg and 6.3 μM Se. Since this protein plays an important role in the methylation process, its suppression in the presence of Se brings a possible explanation for the antagonism between Se and Hg in natural systems. The experiment involving the determination of Hg and Se in membrane proteins separated by 1D gel thin-layer isoelectric focusing revealed that when both elements were present in a culture, the concentration of Hg in the separated proteins was significantly lower in comparison to those without added Se to the culture and vice versa. Finally, near-edge X-ray absorption spectroscopy and extended X-ray absorption fine structure were used to corroborate the presence of a very inert solid HgSe in the cell membrane obtained from the culture containing 0.5 μM Hg and 6.3 μM Se. This confirms the protective effect of Se against Hg assimilation at the molecular level and reinforces the findings of our research group in numerous field and laboratory studies.
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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 | 0.001 |
| 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".