Use of PCR-Targeted Mutagenesis To Disrupt Production of Fusaricidin-Type Antifungal Antibiotics in <i>Paenibacillus polymyxa</i>
Bibliographic record
Abstract
Paenibacillus polymyxa (formerly Bacillus polymyxa) PKB1 has been identified as a potential agent for biocontrol of blackleg disease of canola, caused by the pathogenic fungus Leptosphaeria maculans. The factors presumed to contribute to disease suppression by strain PKB1 include the production of fusaricidin-type antifungal metabolites that appear around the onset of bacterial sporulation. The fusaricidins are a family of lipopeptide antibiotics consisting of a beta-hydroxy fatty acid linked to a cyclic hexapeptide. Using a reverse genetic approach based on conserved motifs of nonribosomal peptide synthetases, a DNA fragment that appears to encode the first two modules of the putative fusaricidin synthetase (fusA) was isolated from PKB1. To confirm the involvement of fusA in production of fusaricidins, a modified PCR targeting mutagenesis protocol was developed to create a fusA mutation in PKB1. A DNA fragment internal to fusA was replaced by a gene disruption cassette containing two antibiotic resistance genes for independent selection of apramycin resistance in Escherichia coli and chloramphenicol resistance in P. polymyxa. Inclusion of an oriT site in the disruption cassette allowed efficient transfer of the inactivated fusA allele to P. polymyxa by intergeneric conjugation. Targeted disruption of fusA led to the complete loss of antifungal activity against L. maculans, suggesting that fusA plays an essential role in the nonribosomal synthesis of fusaricidins.
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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 | 0.000 |
| 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 | 0.001 |
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".