All cellular life-from humans to bacteria-possesses two layers of immunity: innate and adaptive. Scientists have long understood how these two types of immunity work together in higher organisms but not in the microbial world.

Bacteria and archaea use CRISPR-Cas as their sole form of adaptive immunity-a precise, sequence-specific defense that remembers past invaders. But what about innate immunity? Now, a study led by Prof. LI Ming from the Institute of Microbiology of the Chinese Academy of Sciences (CAS) reveals that CRISPR-Cas plays a broader role. Rather than acting alone like a solitary sniper shooting at phages, it also serves as a central command center, directing a network of diverse innate immune systems.

This work was published in Nature on July 22.