We’ve all experienced the nuisance sting of a paper cut, but that tiny skin tear is a signal to the body’s immune system that a battle is beginning. As our bodies enlist the power of our immune systems to thwart bacterial invaders attempting to gain entry, the bacteria are employing defenses of their own.

These countermeasures, known as CRISPR-Cas systems, protect the bacteria from virus invasion, much like vaccines protect against disease. For researchers, exploring the cellular mechanics of bacteria defenses can uncover ways to help the human immune system more efficiently fight off infection.