A Bacterial Signal Transduction System Controls Genetic Exchange and Motility
Bibliographic record
Abstract
The bacterium Rhodobacter capsulatus is capable of an unusual form of genetic exchange, mediated by a transducing bacteriophage-like particle called the gene transfer agent (GTA). GTA production by R. capsulatus is controlled at the level of transcription by a cellular two-component signal transduction system that includes a putative histidine kinase (CckA) and response regulator (CtrA). We found that, in addition to regulating genetic exchange by R. capsulatus, this signal transduction system controls motility. As with the regulation of GTA production, the control of motility by CckA and CtrA occurs through modulation of gene transcription. Disruptions of the cckA and ctrA genes resulted in a loss of class II, class III, and class IV flagellar gene transcripts, suggesting that cckA and ctrA function in motility as class I flagellar genes. We also found that, analogous to the GTA genes, transcription of R. capsulatus flagellar genes appears to be growth phase dependent: class II flagellar gene transcripts are maximal in the mid-log phase of the culture growth cycle, whereas class III gene transcripts are maximal in the late-log phase of growth. We speculate that coordinate regulation of motility and GTA-mediated genetic exchange in R. capsulatus exists because these two processes are complementary mechanisms for cells to cope with unfavorable conditions in natural environments.
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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".