A biomechanical mechanism for initiating DNA packaging
Bibliographic record
Abstract
The bacterial chromosome is under varying levels of mechanical stress due to a high degree of crowding and dynamic protein-DNA interactions experienced within the nucleoid. DNA tension is difficult to measure in cells and its functional significance remains unclear although in vitro experiments have implicated a range of biomechanical phenomena. Using single-molecule tools, we have uncovered a novel protein-DNA interaction that responds to fluctuations in mechanical tension by condensing DNA. We combined tethered particle motion (TPM) and optical tweezers experiments to probe the effects of tension on DNA in the presence of the Hha/H-NS complex. The nucleoid structuring protein H-NS is a key regulator of DNA condensation and gene expression in enterobacteria and its activity in vivo is affected by the accessory factor Hha. We find that tension, induced by optical tweezers, causes the rapid compaction of DNA in the presence of the Hha/H-NS complex, but not in the presence of H-NS alone. Our results imply that H-NS requires Hha to condense bacterial DNA and that this condensation could be triggered by the level of mechanical tension experienced along different regions of the chromosome.
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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 | 0.001 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.001 | 0.000 |
| Insufficient payload (model declined to judge) | 0.002 | 0.001 |
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".