Products of trace methane oxidation during nonmethyltrophic growth by <i>Methanosarcina</i>
Bibliographic record
Abstract
Our understanding of the metabolic pathways involved in the anaerobic oxidation of methane (AOM) is challenged by not having an isolated anaerobic methanotroph. Fortunately, trace methane oxidation (TMO) is carried out by isolated organisms closely related to anaerobic methanotrophs. As TMO likely shares metabolic similarities with the AOM metabolism, studies of TMO in culture experiments can serve to enhance our understanding of AOM. Here we explored TMO in cultures of Methanosarcina acetivorans grown separately on acetate and carbon monoxide. We observed no methane oxidation to carbon dioxide in the cultures grown on acetate, but did observe methane oxidation to acetate (1.1 × 10−6 ± 3.5 × 10−8 moles CH4 oxidized, 0.10% of the CH4 produced). Methane was exclusively converted to the methyl position. Because AOM lipids exhibit strong 13C depletion in nature, our results imply acetate does not play a major role as an AOM intermediate. The carbon monoxide cultures showed little or no methane conversion to carbon dioxide (1.9 × 10−7 ± 2.0 × 10−7 moles CH4 oxidized), moderate methane oxidation to acetate (1.8 × 10−7 ± 7.3 × 10−8 moles CH4 oxidized, 0.14% of biogenic CH4 production), and high methane conversion to the methyl groups of product methyl sulfides (4.0 × 10−6 ± 7.7 × 10−7 moles CH4 oxidized, 3.1% of biogenic CH4 production). Taken together, our results identify methyl sulfides as more likely intermediates in natural AOM than acetate.
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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".