The two chemotaxis in <i>Caulobacter crescentus</i> operons play different roles in chemotaxis and biofilm regulation
Bibliographic record
Abstract
ABSTRACT The holdfast polysaccharide adhesin is crucial for irreversible cell adhesion and biofilm formation in Caulobacter crescentus . Holdfast production is tightly controlled via developmental regulators, and environmental and physical signals. Here we identified a novel mechanism of holdfast production regulation that involves chemotaxis proteins. We characterized the two identified chemotaxis operons of C. crescentus and showed that only the previously characterized, major operon is involved in chemotactic response towards different carbon sources. However, both chemotaxis operons encoded in the C. crescentus genome play a role in biofilm formation and holdfast production, by regulating the expression of hfiA , the gene encoding the holdfast inhibitor HfiA. We show that CheA and CheB proteins act in an antagonistic manner: while the two CheA proteins negatively regulate hfiA expression, the CheB proteins are positive regulators, thus providing a modulation of holdfast synthesis and surface attachment. IMPORTANCE Chemosensory pathways are major signal transduction mechanisms in bacteria. These systems are involved in chemotaxis and other cell responses to environment conditions, such as production of adhesins that enable irreversible adhesion to a surface and surface colonization. The C. crescentus genome encodes two complete chemotaxis operons. Here we characterized the second, novel chemotaxis-like operon. While only the major chemotaxis operon is involved in chemotaxis, both chemotaxis systems modulate C. crescentus adhesion by controlling expression of the holdfast synthesis inhibitor, HfiA. Thus, we identified a new level in holdfast regulation, providing new insights into the control of adhesin production that leads to the formation of biofilms.
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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) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.001 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.001 | 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".