Genetic engineering of <i>Acidithiobacillus ferridurans</i> with CRISPR-Cas9/dCas9 systems
Bibliographic record
Abstract
Abstract Genus Acidithiobacillus includes a group of Gram-negative Fe/S-oxidizing acidophilic chemolithotrophic bacteria that are extensively studied and used for biomining processes. Synthetic biology approaches are key means to study and improve their biomining performance. However, efficient genetic manipulations in Acidithiobacillus are still major bottlenecks. In this study, we report a simple and efficient pAFi system (CRISPR-dCas9) and a scarless pAF system (CRISPR-Cas9) for genetic manipulations in A. ferridurans JAGS. The pAFi system harboring both dCas9 and sgRNA was constructed based on pBBR1MCS-2 to knockdown HdrA and TusA genes, separately, of which the transcription levels were significantly downregulated by 48% and 93%, separately. The pAF system carrying pCas9-sgRNA-homology arms was constructed based on pJRD215 to delete HdrB3 gene and overexpress Rus gene. Our results demonstrated that the pAF system is a fast and efficient genome editing method with an average rate of 15-20% per transconjugant in one recombination event, compared to 10 -3 and then 10 -2 in two recombination events by traditional markerless engineering strategy. Moreover, with these two systems, we successfully regulated iron and sulfur metabolisms in A. ferridurans JAGS: the deletion of HdrB3 reduced 48% of sulfate production, and substitution overexpression of Rus promoter showed 8.82-fold of mRNA level and enhanced iron oxidation rate. With these high-efficient genetic tools for A. ferridurans , we will be able to study gene functions and create useful recombinants for biomining applications. Moreover, these systems could be extended to other Acidithiobacillus strains and promote the development of synthetic biology-assisted biomining. Highlights Two shuttle vectors were constructed for Acidithiobacillus ferridurans All-in-one pAFi (CRISPR-dCas9) and pAF (CRISPR-Cas9) systems were built up for gene knockdown and genome editing, separately The transcription levels of HdrA and TusA were reduced 48% and 93% using pAFi system and thus suppressed sulfur oxidation HdrB3 deletion and Rus overexpression were achieved using pAF system and showed significant effects on sulfur and iron oxidation respectively Our pAF system facilitated genome editing in Acidithiobacillus ferridurans with high efficiency (15-20%) in less than 4 weeks
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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 | 0.001 | 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".