How the other half lives: CRISPR-Cas's influence on bacteriophages

TL;DR

This paper reviews how CRISPR-Cas systems in bacteria and archaea adapt to and combat phage threats, exploring mechanisms of phage evasion and the evolutionary arms race between phages and prokaryotes.

Contribution

It synthesizes recent research on phage evasion strategies and conditions for coexistence with CRISPR-protected hosts, advancing understanding of microbial immune interactions.

Findings

Phages develop mechanisms to evade CRISPR-Cas defenses.

CRISPR-Cas systems influence phage evolution.

Conditions for stable coexistence are identified.

Abstract

CRISPR-Cas is a genetic adaptive immune system unique to prokaryotic cells used to combat phage and plasmid threats. The host cell adapts by incorporating DNA sequences from invading phages or plasmids into its CRISPR locus as spacers. These spacers are expressed as mobile surveillance RNAs that direct CRISPR-associated (Cas) proteins to protect against subsequent attack by the same phages or plasmids. The threat from mobile genetic elements inevitably shapes the CRISPR loci of archaea and bacteria, and simultaneously the CRISPR-Cas immune system drives evolution of these invaders. Here we highlight our recent work, as well as that of others, that seeks to understand phage mechanisms of CRISPR-Cas evasion and conditions for population coexistence of phages with CRISPR-protected prokaryotes.