CRISPR/Cas9 Knockout Studies Implicate Phenazine-1-carboxylic Acid, but Not 2-Hydroxy Phenazine, in the Biocontrol Activity of Pseudomonas chlororaphis Subsp. phenazini Strain S1Bt23 Against Pythium arrhenomanes (Drechsler)
Bibliographic record
Abstract
Liquid chromatography–mass spectrometry analysis of Pseudomonas chlororaphis subsp. phenazini S1Bt23 extracts detected phenazine-1-carboxylic acid (PCA) and 2-hydroxyphenazine (2-OH-PHZ) as the main phenazine derivatives. We investigated their relative contributions to the antagonistic activity of strain S1Bt23 against Pythium arrhenomanes, a root rot pathogen of corn. CRISPR-Cas9 knockouts were carried out on the phzF gene, required for PCA synthesis, and the phzO gene, which is involved in converting PCA to 2-OH-PHZ. Deletion of the phzF gene abrogated the production of PCA and 2-OH-PHZ, and the ΔphzF mutant lost the antagonism against Pythium arrhenomanes. In contrast, deletion of the phzO gene created a 2-OH-PHZ-negative mutant with intact antagonistic ability. Concordantly, S1Bt23 wild type and the ΔphzO mutant, but not the ΔphzF mutant, significantly bioprotected corn seeds of a susceptible inbred variety, CO441, from P. arrhenomanes. At equimolar amounts of 75 nM, synthetic PCA inhibited Pythium growth, whereas 2-OH-PHZ did not. This highlights the critical contribution of PCA to the biocontrol activity of strain S1Bt23 against P. arrhenomanes. Unexpectedly, deletion of phzO did not result in additional PCA accumulation. This suggests that the conversion of PCA to 2-OH-PHZ by S1Bt23 is a potential protective mechanism against the overproduction of lethal cellular doses. This study paves the way for bioengineering strain S1Bt23 into a more effective biopesticide.
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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) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.000 |
| Bibliometrics | 0.000 | 0.001 |
| Science and technology studies | 0.001 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.000 | 0.001 |
| 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".