The assembly of a hybrid type IV secretion system by a Crohn’s disease-associated Escherichia coli strain
Bibliographic record
Abstract
Type IV secretion systems (T4SSs) are central to bacterial pathogenesis. Traditionally known for facilitating DNA transfer via conjugation, T4SSs also mediate biofilm formation. These biofilms are critical for the fitness of adherent-invasive Escherichia coli (AIEC), which are commonly isolated from Crohn's disease patients and are known for propelling gut inflammation. Many AIEC strains carry F-like plasmids encoding the IncF subgroup of T4SSs. Unlike minimized systems with 12 core components, the IncF family is an expanded T4SS with additional genes that enhance conjugation. Here, we show that a biofilm-forming AIEC strain harbors an unusual IncF plasmid that lacks two conserved components essential for T4SS functionality. This strain forms a natural hybrid T4SS where the missing components are supplied by a co-residing chromosomal T4SS on an integrative and conjugative element (ICE). Biochemical assays reveal that this hybrid T4SS drives pilin polymerization and biofilm formation on epithelial cells. Furthermore, we show that a bacterial subpopulation expresses the IncF and ICE-encoded genes in response to host cells, leading to the assembly of biofilms and enhanced fitness in the gut. These findings uncover crosstalk between two evolutionary distant mobile genetic elements to form a hybrid T4SS that mediates biofilm biogenesis by a Crohn's disease-associated pathogen.
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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 | 0.000 |
| 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".