Bacteria run immune systems of their own, and one called CBASS kills the infected cell before a virus can spread to its neighbors. Samuel Hobbs and Philip Kranzusch at Harvard and Dana-Farber worked out what sets it off. Most bacterial defenses watch for viral DNA or RNA. This one watches for a tool the virus carries. Invading phages bring a protease, an enzyme that cuts proteins, and that protease slices a bacterial sensor. The cut itself is the alarm that switches CBASS on. It is a clever solution to a hard problem, since the defense is lethal and must not fire by accident. The authors show the trigger is widespread across these systems. CBASS is a cousin of the cGAS-STING pathway in our own cells, so the logic may carry lessons for human immunity. The practical hope is better phage therapies, designed to work with these defenses rather than trip them.
Source: Science, 1 October 2026
