Investigating the role of MlaA in SDS-EDTA resistance pathways in Escherichia coli
Bibliographic record
Abstract
The outer membrane (OM) in Gram-negative bacteria, like Escherichia coli, is asymmetric, with mainly lipopolysaccharide (LPS) molecules in the outer leaflet and phospholipids in the inner leaflet. Maintaining structural asymmetry of the OM is vital for cell survival in unfavourable conditions. The Mla pathway is a mechanism that restores membrane asymmetry upon exposure to external stressors, such as sodium dodecyl sulfate (SDS) and ethylenediaminetetraacetic acid (EDTA). Deletion of the OM porin OmpC, which forms a complex with MlaA, a component of the Mla pathway, results in hypersensitivity to SDS-EDTA treatment. However, these mutants are rescued when grown in phosphate deficient conditions. The phosphoporin PhoE, which is upregulated under phosphate limitation, likely complements OmpC for maintaining OM asymmetry. PhoE shares structural and functional similarities to OmpC, but its interaction with MlaA remains unclear. Thus, we sought to investigate the role of MlaA in the OmpC- and putative PhoE- dependent pathways of restoring membrane asymmetry. We hypothesized that since OmpC and PhoE appear to mediate independent pathways for maintaining membrane asymmetry that converge on MlaA, deletion of MlaA would cause severely reduced cell growth compared to both ΔompC and ΔphoE mutants. To test this, we performed growth curve assays with wild type, ΔompC, ΔphoE, and ΔmlaA strains in minimal media containing SDS and increasing concentrations of EDTA. We found that growth of ΔmlaA mutants was not as severely inhibited as expected, and that ΔompC mutants were more sensitive to SDS-EDTA than ΔmlaA mutants, demonstrating the importance of MlaA-independent pathways of SDS-EDTA resistance.
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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 | 0.001 | 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 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".