How bacterial immune systems sense phage infection.

Bacterial immune systems recognize phage infection primarily through detection of phage nucleic acids, proteins, and perturbations to host processes.

• Why it matters: Understanding how bacteria detect phage invasion is crucial for revealing fundamental immune principles and could inform strategies to manipulate bacterial defenses or combat phage infections.
• What they did: The review summarizes experimental approaches that identify phage triggers, categorizing them into three classes—phage nucleic acids, proteins, and host process perturbations—and discusses principles connecting diverse defense mechanisms.
• The result: This framework enhances understanding of bacterial discrimination between self and non-self, emphasizing sensing mechanisms that ensure rapid and robust immune activation.