<i>Lactococcus lactis</i> mutants resistant to lactococcin A and garvicin Q reveal missense mutations in the sugar transport domain of the mannose phosphotransferase system
Bibliographic record
Abstract
ABSTRACT Lactococcin A is a bacteriocin from Lactococcus lactis that permeabilizes the membrane of sensitive lactococcal cells and requires the presence of the membrane-bound components IIC and IID of the mannose phosphotransferase system (man-PTS). Recently, it was reported through cryo-electron microscopy analyses of man-PTS and several bacteriocins fused to a maltose-binding protein, including lactococcin A, that these bacteriocins create pores by inserting themselves between the Core and Vmotif domains of man-PTS. In our study, we obtained a dozen spontaneous mutants of L. lactis IL1403 resistant to lactococcin A. All but one of the mutants of IL1403 have mutations located in the genes encoding the IIC or IID proteins. These mutations also resulted in resistance to garvicin Q, a bacteriocin from Lactococcus garvieae with a broad inhibition spectrum and very little sequence homology to lactococcin A. Missense mutations were found in the sugar transport domain of man-PTS of bacteriocin-resistant IL1403 mutants, which also impeded the uptake of mannose. When lactococcin A, garvicin Q, or pediocin PA-1, an anti-listerial bacteriocin, were fused to a maltose-binding protein, we observed reduced or no antibacterial activity. Taken together, the precise mechanism of action of bacteriocins using the man-PTS remains to be fully understood. IMPORTANCE Many bacteriocins target the sugar transporter mannose phosphotransferase system (man-PTS) to exert their antibacterial activity. The elucidation in recent years of the structure of man-PTS has facilitated our understanding of how bacteriocins might interact with the receptor and which domains of the transporter are involved in bacteriocin resistance. Here, we show that missense mutations in the sugar-binding domain of the man-PTS not only impede the uptake of sugars but also prevent the antibacterial activity of the bacteriocins lactococcin A and garvicin Q.
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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 | 0.001 |
| 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".