Coevolution between bacterial CRISPR-Cas systems and their bacteriophages

CRISPR-Cas systems provide bacteria and archaea with adaptive, heritable immunity against their viruses (bacteriophages and phages) and other parasitic genetic elements. CRISPR-Cas systems are highly diverse, and we are only beginning to understand their relative importance in phage defense. In this review, we will discuss when and why CRISPR-Cas immunity against phages evolves, and how this, in turn, selects for the evolution of immune evasion by phages. Finally, we will discuss our current understanding of if, and when, we observe coevolution between CRISPR-Cas systems and phages, and how this may be influenced by the mechanism of CRISPR-Cas immunity.

Automated summary

CRISPR-Cas systems offer adaptive, heritable immunity to bacteria and archaea against their viruses, but the diversity of these systems and their importance in phage defense are still being understood. This review discusses the evolution of CRISPR-Cas immunity against phages, how this leads to immune evasion by phages, and the potential coevolution between CRISPR-Cas systems and phages.