Periplasmic Events in the Assembly of Bacterial Lipopolysaccharides
Bibliographic record
Abstract
This chapter provides an overview of the assembly pathways for lipopolysaccharide (LPS) molecules, with particular emphasis on reactions and components occurring in the periplasm. Species-specific variations on the generally conserved theme are now being identified. In the current working model, it is proposed that lipid A core binds to MsbA and the polar parts of the exported molecule enter the lumen of the transporter. WecA is an integral membrane protein that forms the undecaprenyl pyrophosphoryl-GlcNAc. The premise for the periplasmic location of the glucosylation reaction is based on studies with Salmonella that first showed undecaprenyl pyrophosphate-linked intermediates provide the acceptor for glucosylation. O-Acetyltransferases also modify O-polysaccharides. Well-documented examples include OafA, which confers O:5 specificity in Salmonella Oac encoded by the Shigella seroconverting bacteriophage SF6 and the O-acetyltransferase carried by Pseudomonas aeruginosa bacteriophage D3. The WbdD-mediated chain termination reactions establish modal regulation in participation with the ABC transporter because the export process is coupled to chain termination. Synthases are processive glycosyltransferases that have the capacity to synthesize polymers within one or more linkages. It has been shown that peptidoglycan is also distributed in a helical arrangement along the side walls of Escherichia coli and it will be interesting to see whether the events are coupled and whether the emerging bacterial cytoskeletal components play any role in dictating the sites of LPS insertion.
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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 | 0.001 | 0.000 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.000 | 0.001 |
| Research integrity | 0.000 | 0.001 |
| Insufficient payload (model declined to judge) | 0.001 | 0.002 |
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".