Related Experiment Video
Updated: Jun 28, 2026
10:52
Precise Phage Mutagenesis with NgTET-Assisted CRISPR-Cas Systems
Published on: October 14, 2025
END nucleases are antiphage defence systems targeting multiple phages with modified genomes.
Wearn-Xin Yee1, Yan-Jiun Lee2, Kira S Makarova3
1Department of Microbiology and Immunology, University of California, San Francisco, CA, USA.
Nature Microbiology
|June 26, 2026
Summary
Researchers discovered a novel defense system in Pseudomonas aeruginosa, called END nucleases, that targets modified phages. This finding is crucial for understanding phage-bacterial interactions and optimizing phage therapy outcomes.
Area of Science:
- Microbiology
- Bacteriology
- Genetics
Background:
- Prokaryotes utilize defense islands for phage immunity, but active systems against specific phages are often unknown.
- Pseudomonas aeruginosa, a bacterium often found in cystic fibrosis patients, interacts with various phages.
Purpose of the Study:
- To identify the specific defense system in Pseudomonas aeruginosa responsible for blocking Pbunavirus phages.
- To characterize the mechanism and specificity of this novel defense system.
Main Methods:
- Genetic analysis to identify the responsible gene within a defense island.
- Biochemical characterization of the identified defense system (END nucleases).
- Testing the activity of END nucleases against various modified phages.
Main Results:
- A single gene encoding END nucleases was identified as essential for blocking Pbunavirus replication.
- END nucleases possess a Type IIS restriction endonuclease-like domain fused to an inactive endonuclease III domain.
- These nucleases broadly target modified phages, irrespective of the specific DNA modification (beyond methylation).
- A specific region within the iEndoIII domain determines targeting specificity.
- Jumbo phages from Pbunavirus and Wroclawvirus families encode inhibitors of END nucleases.
Conclusions:
- END nucleases represent a broad, modification-dependent restriction endonuclease system.
- This system provides insights into phage-bacterial interactions and potential strategies to enhance phage therapy efficacy.
- The identification of phage-encoded inhibitors highlights co-evolutionary dynamics between phages and bacterial defense mechanisms.
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