Discovery of Novel CRISPR-Cas Systems and Implications for the Evolution of Microbial Adaptive Immunity

Class 2 CRISPR-Cas systems are characterized by effector modules that consist of a single multidomain protein, such as Cas9 or Cpf1. We designed a computational pipeline for the discovery of novel class 2 variants and used it to identify six new CRISPR-Cas subtypes. The diverse properties of these new systems provide potential for the development of versatile tools for genome editing and regulation, and several such tools have already been developed starting with the predictions produced using our pipeline. I will present a comprehensive census of Class 2 CRISPR-Cas types and subtypes in complete and draft bacterial and archaeal genomes and outline evolutionary scenarios for the independent origin of different class 2 CRISPR-Cas systems from mobile genetic elements, along with a general concept of evolution of microbial adaptive immunity.