Exploring the ecological function of CRISPR-Cas virus defense

Virus-host interaction is a key process in understanding the ecology and evolution of life. The study of the CRISPR-Cas RNA-guided adaptive immune systems of bacteria and archaea has added to our understanding of the virus defense mechanisms of microorganisms. The molecular details of the CRISPR-Cas systems are well explored and have allowed development a new generation of gene editing tools. However, the actual role and importance of CRISPR-Cas virus defense in nature is complex to study and have attracted less attention. Metagenomic analysis of microbial populations and the study of viruses-host systems in the laboratory have begun to unravel this question. Key findings in the field are described, with focus on recent developments.