Mycobacteriophage Mcgavigan Uses Noncanonical Bxb1‐Like Repressor for Heterotypic Superinfection Immunity
Bibliographic record
Abstract
Mycobacteriophage Mcgavigan could be a promising candidate for use as a preventative agent against infections with Mycobacterium avium subsp. paratuberculosis. Bioinformatic analysis of the Mcgavigan genome revealed the presence of an operon containing a "Bxb1-like" repressor. The operon may have been acquired by the phage through horizontal gene transfer with a Bxb1-like mycobacteriophage in its evolutionary past. We sought to investigate the function of the acquired repressor as a potential regulator of lysogeny or as a source of heterotypic superinfection immunity. Recombineering with CRISPR counter-selection was employed to achieve a clean deletion of the Bxb1-like repressor from Mcgavigan's genome. Integrase was also deleted as a means of creating a lytic-only phage for comparison purposes and the elimination of lysogeny with this edit was confirmed. To test phenotypic changes which resulted from these deletions, several parameters such as burst size, latency period, and killing efficiency were measured for each knockout mutant and lysogeny was tested. The integrase deletion mutant had complete lysogeny abolishment and performed similarly to wild-type phage on all measured parameters. The deletion of the Bxb1-like repressor did not affect the lysogenic capability of the phage. Whereas Mcgavigan lysogens are typically immune to superinfection from Terelak, a mycobacteriophage related to Bxb1, lysogens created from Mcgavigan with the Bxb1-like repressor deletion were completely resensitized to heterotypic superinfection by Terelak. This suggested that this repressor was acquired by Mcgavigan through horizontal gene transfer for the purposes of superinfection immunity against cluster A1 mycobacteriophages and was not used for maintenance of lysogeny.
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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 | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 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".