Characterization of a Stress-Induced Alternate Sigma Factor, RpoS, of <i>Coxiella burnetii</i> and Its Expression during the Development Cycle
Bibliographic record
Abstract
Coxiella burnetii is an obligate intracellular bacterium that resides in an acidified phagolysosome and has a remarkable ability to persist in the extracellular environment. C. burnetii has evolved a developmental cycle that includes at least two morphologic forms, designated large cell variants (LCV) and small cell variants (SCV). Based on differential protein expression, distinct ultrastructures, and different metabolic activities, we speculated that LCV and SCV are similar to typical logarithmic- and stationary-phase growth stages. We hypothesized that the alternate sigma factor, RpoS, a global regulator of genes expressed under stationary-phase, starvation, and stress conditions in many bacteria, regulates differential expression in life cycle variants of C. burnetii. To test this hypothesis, we cloned and characterized the major sigma factor, encoded by an rpoD homologue, and the stress response sigma factor, encoded by an rpoS homologue. The rpoS gene was cloned by complementation of an Escherichia coli rpoS null mutant containing an RpoS-dependent lacZ fusion (osmY::lacZ). Expression of C. burnetii rpoS was regulated by growth phase in E. coli (induced upon entry into stationary phase). A glutathione S-transferase-RpoS fusion protein was used to develop polyclonal antiserum against C. burnetii RpoS. Western blot analysis detected abundant RpoS in LCV but not in SCV. These results suggest that LCV and SCV are not comparable to logarithmic and stationary phases of growth and may represent a novel adaptation for survival in both the phagolysosome and the extracellular environment.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| 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 teacher head, 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".