University of Utah researchers and collaborators have shown that a phage enzyme can cut a bacterial sensor, activating the CBASS immune system and forcing an infected cell to self-destruct before the virus spreads.
The study, published in Science on October 1, 2026, explains how bacteria detect phage attacks through a mechanism scientists had not previously understood. Phages are viruses that infect bacteria and are being studied as potential treatments for antibiotic-resistant infections. When certain phages invade, they produce proteases—enzymes that break down proteins—including the T4 phage’s prohead protease.
Researchers found that the enzyme cuts an exposed activation loop on a bacterial CD-NTase sensor, switching it on and prompting the production of molecular signals. Those signals activate CBASS, a “last resort” defense that kills the host bacterium before newly produced phages can escape and infect neighboring cells. The findings indicate that CBASS recognizes the destruction of a virus-dependent protein rather than detecting viral genetic material directly.
Scientists say the discovery could help guide the design of phage therapies that bypass bacterial defenses and may also shed light on immune pathways related to the human cGAS-STING system.