The arms race between bacteria and the viruses that infect them brought the Cas9 and similar editing systems. These enzymes are essentially a bacterial immune system, and now are being exploited as important tools in genetic engineering. To counter the bacteria response viruses produce inhibitors of the Cas enzymes. Dr. Joseph Bondy-Denomy is a professor at the University of California San Francisco that studies these inhibitors. He discusses their discovery and potential applications. Listen to Talking Biotech Podcast #227 here.