Effect of short-chain fatty acids and pH on aerobic and anaerobic growth of Pseudomonas aeruginosa
Bibliographic record
Abstract
Background: Pseudomonas aeruginosa (PA) is one of the most common pathogens in patients with cystic fibrosis (CF) lung disease. PA and other anaerobic bacteria produce short-chain fatty acids (SCFAs) as byproducts of anaerobic fermentation. SCFAs are more volatile at low pH values, and reports have shown that CF patient sputum in acidic. Recently, we detected SCFAs in the low millimolar range in the sputum of CF patients. Aim: To determine if SCFAs affect bacterial growth at different pH levels. Methods: The laboratory strain PAO1 and a clinical isolate PA508 were used for experiments with and without the addition of SCFAs (acetate, propionate, butyrate) at a range of concentrations between 3.125-100 mM and pH values from 5.5-7.0 in tryptic soy broth. Optical density at 600 nm was measured every 30 minutes for a 6 hour period, as well as viable colony counts after the period of incubation. Anaerobic/microaerobic conditions were generated by sealing microplates with optically-clear PCR film. Results: Acetate showed a significant inhibition in growth above 50 mM (>77%, p 20%, p<0.05). Propionate had the highest inhibition, followed by butyrate and acetate. Anaerobic conditions resulted in lower growth overall and showed similar trends in growth inhibition. Results were consistent for both PA strains tested. Conclusion: SCFAs increase the growth of laboratory and clinical strains of PA at concentrations found in CF patient sputum, but inhibit growth at high concentrations. SCFAs produced by anaerobic bacteria may provide an indication of increased virulence of PA.
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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".