The immobilization of gold from gold (III) chloride by a halophilic sulphate-reducing bacterial consortium
Bibliographic record
Abstract
Abstract A consortium containing halophilic, dissimilatory sulphate-reducing bacteria was enriched from Basque Lake #1, located near Ashcroft, British Columbia, Canada to evaluate the role these bacteria have on the immobilization of soluble gold. The consortium immobilized increasing amounts of gold from gold (III) chloride solutions, under saline to hypersaline conditions, over time. Gold (III) chloride was reduced to elemental gold in all experimental systems. Salinity did not affect gold immobilization. Scanning electron microscopy and transmission electron microscopy demonstrated that reduced gold (III) chloride was immobilized as c. 3–10 nm gold colloids and c. 100 nm colloidal aggregates at the fluid–biofilm interface. The precipitation of gold at this organic interface protected cells within the biofilm from the ‘toxic effect’ of ionic gold. Analysis of these experimental systems using X-ray absorption near-edge spectroscopy confirmed that elemental gold with varying colloidal sizes formed within minutes. The immobilization of gold by halophilic sulphate-reducing bacteria highlights a possible role for the biosphere in ‘intercepting’ mobile gold complexes within natural, hydraulic flow paths. Based on the limited toxicity demonstrated in this experimental model, significant concentrations of elemental gold could accumulate over geological time in natural systems where soluble gold concentrations are more dilute and presumably ‘non-toxic’ to the biosphere.
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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 | 0.001 | 0.001 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.001 | 0.000 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.001 | 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".