A compact Druantia defense clears phage infections via single-stranded DNA recognition and directional duplex unwinding.

A compact type III-A Druantia system uses single-stranded DNA recognition and directional unwinding to effectively clear phage infections in bacteria.

• Why it matters: Understanding bacterial defense mechanisms against phages is crucial for developing new antimicrobial strategies and managing phage resistance. Many systems rely on complex or less specific cues, so identifying a simple, efficient trigger like exposed single-stranded DNA fills an important knowledge gap.
• What they did: Researchers examined the Druantia system from Escherichia coli, focusing on its two proteins, DruE and DruH, and demonstrated that DruE unwinds DNA in a 3'-to-5' direction upon sensing exposed single-stranded regions, facilitating phage clearance.
• The result: This discovery shows that exposed single-stranded DNA activates bacterial immunity via a specialized helicase activity, providing insights into a streamlined, effective anti-phage defense mechanism.