Heavy metal(loid) transformations by bacteria isolated from extreme environments
Bibliographic record
Abstract
The research presented here studied bacteria from extreme environments possessing strong resistance to highly toxic oxyanions of Te, Se, and V. The impact of tellurite on cells of aerobic anoxygenic phototrophs and heterotrophs from freshwater and marine habitats was investigated. Physiological responses of cells to TeO32- varied. In its presence, biomass either increased, remained similar or decreased, with ATP production following the same trend. Four detoxification strategies were observed: 1) Periplasmic based reduction; 2) Reduction needing an intact cytoplasmic membrane; 3) Reduction involving an undisturbed whole cell; and 4) Membrane associated reduction. The first three require de novo protein synthesis, while the last was constitutively expressed. We also investigated two enzymes responsible for tellurite reduction. The first came from the periplasm of deep-ocean hydrothermal vent strain ER-Te-48 associated with tube worms. The second was a membrane associated reductase from Erythromonas ursincola, KR99. Both could also use tellurate as a substrate. ER-Te-48 also has a second periplasmic enzyme which reduced selenite. Additionally, we set out to find new organisms with the ability to resist and reduce Te, Se, and V oxyanions, as well as use them for anaerobic respiration. New strain CM-3, a Gram negative, rod shaped bacterium from gold mine tailings of the Central Mine in Nopiming Provincial Park, Canada, has very high level resistance and the capability to perform dissimilatory anaerobic reduction of tellurite, tellurate, and selenite. Its partial 16S rRNA gene sequencing revealed a 99.0% similarity to Pseudomonas reactans. We also discovered that the epibiotic bacterial community associated with tube worms living in the vicinity of deep sea hydrothermal vents of the Juan de Fuca Ridge in the Pacific Ocean can respire anaerobically on tellurite, tellurate, selenite, selenate, metavanadate and/or orthovanadate. Out of 107 isolates tested, 106 were capable of respiration on one or more of the oxyanions. Based on partial 16S rRNA gene sequences, the bacterial community is phylogenetically and taxonomically highly diverse.
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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 | 0.001 | 0.000 |
| Open science | 0.000 | 0.001 |
| 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".