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Updated: May 17, 2026
10:52
Precise Phage Mutagenesis with NgTET-Assisted CRISPR-Cas Systems
Published on: October 14, 2025
Phage mutations in response to CRISPR diversification in a bacterial population
Christine L Sun1, Rodolphe Barrangou, Brian C Thomas
1University of California, Berkeley, CA, USA. christine_sun@berkeley.edu
Environmental Microbiology
|October 13, 2012
Summary
Bacteria and phage co-evolution rapidly drives host immunity through CRISPR spacer acquisition. Phage mutations in the proto-spacer adjacent motif (PAM) allowed rapid escape from host defenses, demonstrating strong selective pressures.
Area of Science:
- Microbial Ecology
- Evolutionary Biology
- Genetics
Background:
- Interactions between bacteria and phages are crucial for microbial evolution and ecosystem function.
- Host-phage dynamics are shaped by immunity and infectivity, with constant evolutionary arms races.
- CRISPR-Cas systems provide adaptive immunity in bacteria against phages.
Purpose of the Study:
- To investigate the co-evolutionary processes between Streptococcus thermophilus and phage 2972.
- To track the diversification of CRISPR (clustered regularly interspaced short palindromic repeats) and host-phage interactions.
- To identify genetic adaptations in both host and phage populations under selective pressure.
Main Methods:
- Co-culturing of Streptococcus thermophilus DGCC7710 with phage 2972.
- Metagenomic sequencing (454 FLX Titanium) of host-phage populations after one week.
- Comparative genomic analysis to identify new CRISPR spacers and phage single-nucleotide polymorphisms (SNPs).
Main Results:
- CRISPR spacer acquisition led to a genetically diverse host population with multiple subdominant lineages.
- Phage mutations conferring resistance were primarily located in or near the proto-spacer adjacent motif (PAM).
- Severe selective events resulted in the rapid fixation of specific phage genotypes, potentially carrying additional traits.
Conclusions:
- CRISPR-mediated immunity drives rapid bacterial population diversification.
- Phage adaptation via mutations in the PAM region is a critical mechanism for overcoming host immunity.
- Co-evolutionary dynamics between hosts and phages are characterized by intense selective pressures and rapid genetic adaptation.
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