CAS9 is a novel DNA-cutting enzyme that is the main component of an intrinsic DNA editing system used by bacteria to kill attacking viruses. Clustered regularly interspaced short palindromic repeats (CRISPR) are distinct features of most bacterial genomes, and thought to be involved in resistance to bacteriophages. CRISPR is a primitive immune system of sorts that determines resistance specificity, as published by the Danisco Corporation in Science1.
