Function of penicillin-binding protein 2 in viability and morphology of Pseudomonas aeruginosa
Bibliographic record
Abstract
OBJECTIVES: To investigate the function of penicillin-binding protein 2 (PBP 2) in Pseudomonas aeruginosa PAO1. METHODS: The growth and morphology of P. aeruginosa cultured in the absence and presence of mecillinam was assessed. The gene encoding PBP 2, pbpA, was identified in the genome of P. aeruginosa PAO1 and both its full-length and an engineered truncated form were cloned and expressed in Escherichia coli. Site-directed mutagenesis was used to confirm Ser-327 as the catalytic nucleophile of its transpeptidase domain. Allelic exchange was used to construct a chromosomal mutant of pbpA in strain PAO1. RESULTS: PAO1 grew with a spherical morphology in the presence of mecillinam at concentrations as high as 2000 mg/L. Both wild-type and truncated, soluble forms of PBP 2 were shown to bind penicillins and a competition assay demonstrated their specificity for mecillinam. The PAO1 DeltapbpA insertional mutant also grew as spheres, and complementation with a plasmid encoding active pbpA, but not with an inactive Ser-327 --> Ala derivative, restored rod-shape morphology. MIC values of a variety of beta-lactams were significantly lower for the insertional mutant compared with wild-type PAO1. The muropeptide profile of peptidoglycan from PAO1 DeltapbpA analysed by HPLC/MALDI TOF MS indicated wild-type levels of cross-linking despite the loss of PBP 2 transpeptidase activity. CONCLUSIONS: PBP 2 in P. aeruginosa is responsible for the rod-shape morphology of the cells and contributes significantly to beta-lactam resistance. The viability of cells lacking an active PBP 2 suggests that the organization of the peptidoglycan biosynthetic machinery is different in this pathogen compared with E. coli.
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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 | 0.001 | 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".