Researchers have found the trigger behind a powerful bacterial defense against viruses.

Viruses that prey on bacteria could become an increasingly important tool for treating bacterial infections, particularly as antibiotic resistance makes some infections harder to control. These viruses, known as bacteriophages (phages), can infect and destroy harmful bacteria without damaging human cells.

Using phages as treatments, however, comes with a major challenge. Bacteria are not defenseless against viruses. They possess their own immune systems, and understanding those defenses could help scientists design phage therapies that are better able to overcome them.