DNA polymerase I is required for the Hachiman-family anti-phage defense system.

DNA polymerase I (PolA) is essential for Hachiman-family anti-phage defense, enabling phage restriction and growth arrest in Escherichia coli, with a critical role for its exonuclease domain.

• Why it matters: Understanding how bacterial defense systems coordinate with host DNA replication and repair is crucial for revealing mechanisms of phage resistance and preventing self-damage during uninfected growth.
• What they did: The study used a temperature-sensitive polA mutant and biochemical assays to show that PolA interacts with the AbpAB complex and is necessary for phage restriction and DNA damage-induced growth arrest, while RNase HI prevents toxicity in uninfected cells.
• The result: Findings demonstrate that host DNA replication enzymes support anti-phage defense and safeguard against self-inflicted growth inhibition, highlighting potential targets for modulating bacterial immunity.