antiphage

Antiphage refers to the set of biological strategies used by bacteria and archaea to prevent, resist, or mitigate infection by bacteriophages (phages). These defense systems protect hosts during phage attacks and are a major driver of microbial evolution, contributing to the dynamic interactions that shape microbial communities.

Antiphage defenses include both innate-like and adaptive mechanisms. The CRISPR-Cas systems provide adaptive immunity by recording phage DNA sequences and guiding nucleases to cleave matching invaders. Other defense layers include restriction-modification systems that cut unmethylated phage DNA, and abortive infection or toxin-antitoxin systems that halt phage propagation or kill infected cells to protect the population. Additional systems such as BREX, DISARM, CBASS and retron-based defenses contribute diverse molecular strategies to recognize and neutralize phages.

Phages counteract antiphage defenses by deploying anti-CRISPR proteins that inhibit bacterial immune components, altering their host receptors to prevent adsorption, or evolving genome features to evade detection by host systems. The ongoing arms race drives rapid evolution on both sides and fosters substantial genetic diversity in microbial ecosystems.

Knowledge of antiphage systems has practical implications. In phage therapy, understanding bacterial defenses helps in selecting or engineering phages with improved efficacy. In biotechnology, CRISPR-derived tools and other defense components are harnessed for genome editing and regulation, while strategies to overcome antiphage defenses inform industrial biotechnology and probiotic applications.

Research on antiphage systems continues to uncover new defense pathways and cross-talk between systems, with metagenomic data revealing a vast, largely uncharacterized diversity. While well characterized in model bacteria, the full spectrum of antiphage strategies remains an active area of microbiology.