Visualization of syntrophic benzene-fermenting <i>Desulfobacterota</i> ORM2 in a methanogenic enrichment culture using fluorescence <i>in situ</i> hybridization
Bibliographic record
Abstract
Abstract Although benzene degradation under strictly anoxic conditions was first reported over 25 years ago, the mechanism for benzene activation in the absence of oxygen is still elusive. A major limitation has been the difficulty to grow anaerobic benzene-degrading enrichment cultures. Our laboratory has maintained a methanogenic enrichment culture for decades, harboring a benzene fermenter referred to as Desulfobacterota ORM2. Recent genomic analyses indicate that ORM2 is not affiliated with any characterized genus, but it is phylogenetically similar to several other known and predicted benzene degraders. Desulfobacterota ORM2 has a doubling time of approximately 30 days and often enters a long lag or decay phase after inoculation into sterile pre-reduced anaerobic medium. A specific fluorescent in situ hybridization (FISH) probe was used to observe Desulfobacterota ORM2 cells during this decay phase, revealing a rod-shaped cell of variable length with a tendency to associate with other cells, particularly methanogens. Microscopic and genomic analyses indicate that Desulfobacterota ORM2 may produce extracellular polymeric substances (EPS) that likely contribute to cell aggregation. The production of EPS may consume a significant amount of energy, perhaps contributing to the lag time before onset of growth of Desulfobacterota ORM2 post-inoculation. We observed little cell aggregation in a culture amended with very high concentrations of benzene (90-120 mg/L). This study visualized the cells of a novel clade within the Desulfobacterota for the first time, enabling monitoring of spatial organization within a methanogenic consortium and provides hints to improve the growth rate of ORM2. Importance A specific FISH probe was designed for the poorly characterized benzene fermenter Desulfobacterota ORM2. This probe was used to monitor changes in spatial organization in a methanogenic benzene-degrading enrichment culture. ORM2 cells were often found in cell aggregates, revealing a possible reason for the long lag phases observed after inoculation.
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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) | 0.001 | 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".