ArdC, a ssDNA-binding protein with a metalloprotease domain, overpasses the recipient hsdRMS restriction system broadening conjugation host range
Bibliographic record
Abstract
Plasmids, when transferred by conjugation in natural environments, must overpass restriction-modification systems of the recipient cell.We demonstrate that protein ArdC, encoded by broad host range plasmid R388, was required for conjugation from Escherichia coli to Pseudomonas putida.Expression of ardC was required in the recipient cells, but not in the donor cells.Besides, ardC was not required for conjugation if the hsdRMS system was deleted in P. putida recipient cells.ardC was also required if the hsdRMS system was present in E. coli recipient cells.Thus, ArdC has antirestriction activity against the HsdRMS system and consequently broadens R388 plasmid host range.The crystal structure of ArdC was solved both in the absence and presence of Mn 2+ .ArdC is composed of a non-specific ssDNA binding N-terminal domain and a C-terminal metalloprotease domain, although the metalloprotease activity was not needed for the antirestriction function.We also observed by RNA-seq that ArdC-dependent conjugation triggered an SOS response in the P. putida recipient cells.Our findings give new insights, and open new questions, into the antirestriction strategies developed by plasmids to counteract bacterial restriction strategies and settle into new hosts. Author summaryHorizontal gene transfer is the main mechanism by which bacteria acquire and disseminate new traits, such as antibiotic resistance genes, that allow adaptation and evolution.Here we identified a gene, ardC, that enables a plasmid to increase its conjugative host range, and thus positively contributes to plasmid fitness.The crystal structure of the antirestriction protein ArdC revealed a fold different from other antirestriction proteins.Our results have wide implications for understanding how a gene enlarges the environments a plasmid can colonize and point to new targets to harness the bacterial DNA uptake control.
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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 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.001 |
| Research integrity | 0.000 | 0.001 |
| Insufficient payload (model declined to judge) | 0.001 | 0.001 |
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".