Diversity and evolution of class 2 CRISPR–Cas systems

Class 2 CRISPR–Cas systems are characterized by effector modules that consist of a single multidomain protein. In this Analysis, using a computational pipeline, the authors discover three novel families of class 2 effectors that correspond to three new CRISPR–Cas subtypes and present a comprehensive census of class 2 systems that are encoded in complete and draft bacterial and archaeal genomes.