Nutritional cues in cystic fibrosis sputum regulate number and functioning of flagella through flhF and c-di-GMP-related protein BCAL1069 in Burkholderia cenocepacia K56-2
Bibliographic record
Abstract
Burkholderia cenocepacia infections in the lungs of cystic fibrosis (CF) patients are difficult to treat due to resistance to multiple antibiotics, implying the need to identify new therapeutic targets to eradicate lung infections. The sputum of CF patients is rich in amino acids and was previously shown to increase flagellar gene expression in B. cenocepacia. However, the molecular mechanisms by which B. cenocepacia regulates swimming motility and flagellar biosynthesis are not understood. In the first part of this thesis, I elucidate how CF sputum conditions regulate swimming motility and flagellar biosynthesis in B. cenocepacia K56-2. Electron microscopy and flagella staining of B. cenocepacia demonstrated that the increased motility and flagellin corresponds to multiple flagella expressed under CF sputum conditions. I created a deletion ∆flhF mutant that exhibited downregulation in flagellin expression and displayed 80% aflagellated bacterial subpopulations. These results demonstrate that CF sputum nutritional conditions regulate flagellin and flagellation pattern through flhF in B. cenocepacia K56-2. In the second part of the thesis, I investigated the role of c-di-GMP metabolizing genes in the swimming motility of B. cenocepacia K56-2 in CF sputum conditions. Overexpression of the wspR gene that causes an increase in c-di-GMP levels resulted in a significant reduction in the motility of B. cenocepacia K56-2. The increased c-di-GMP levels did not affect flagellin expression and flagellar biosynthesis. Screening of the putative c-di-GMP genes insertional mutants for defective motility led us to identify a BCAL1069 gene, which encodes a protein with a putative sensory signaling PAS domain, and c-di-GMP metabolizing GGDEF and EAL domains. Further, the reduced swimming motility of the BCAL1069 mutant was evident in CF nutritional conditions and in the presence of arginine and glutamate. The increase in intracellular c-di-GMP levels in the BCAL1069 mutant indicated that BCAL069 possesses an EAL domain (phosphodiesterase) activity. Thus it appears that BCAL1069 mediates swimming motility of B. cenocepacia K56-2 in response to CF sputum nutritional cues by changing intracellular c-di-GMP levels. Taken together, the findings of this thesis suggest that CF sputum conditions regulate number and functioning of flagella in B. cenocepacia K56-2 through the flhF and BCAL1069 genes, respectively.
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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 | 0.001 |
| 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".