A role for rhamnolipid in biofilm dispersion
Bibliographic record
Abstract
Biofilms are often considered as localized zones of high cell density. Quorum sensing provides a means for control of population processes and has been implicated in the regulation of biofilm activities. We present a role for quorum sensing in programmed detachment and dispersal processes. Biofilms of Pseudomonas aeruginosa PAO1 and its isogenic homoserine lactone (HSL) mutant P. aeruginosa PAO-JP2 were grown in batch culture on glass substrata; differences were found in the rate and extent of formation of biofilm. Climax communities were observed for PAO1 at 24 h. These were later accompanied by foaming, a drop in the surface tension of culture media and dispersal of the biofilm, after which no subsequent biofilm accretion occurred. PAO-JP2 cultures reformed biofilm post-detachment and did not foam. Prevention of biofilm reformation in the wild type was related to some component excreted into the culture medium. Rhamnolipid, a biosurfactant regulated by quorum sensing, was detected in PAO1 cultures. When rhamnolipid was added to freshly inoculated substrata, biofilm formation was inhibited. At 20 h, PAO1 biofilms were transferred to medium with added rhamnolipid: biofilm was relatively unaffected. Biofilm events were also studied in medium supplemented with N-butyryl-L-homoserine lactone, which is involved in the regulation of rhamnolipid synthesis. Both strains exhibited similar trends of rapid biofilm formation and dramatic changes in the rate and extent of biofilm accretion. In both cases, there was premature foaming, lowered surface tension and elevated rhamnolipid levels. A role for HSLs in maintenance of biofilm and events leading to dispersion of cells is proposed. This role would encompass dispersion but not necessarily detachment of cells from biofilm and supports a new function for rhamnolipid in pathogenesis, whereby rhamnolipid would promote the dissemination of cells from a nidus of infection.
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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 | 0.001 | 0.001 |
| Open science | 0.000 | 0.001 |
| Research integrity | 0.001 | 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".