Manganese activates the CBASS immunity to protect bacteria from phage infection

ABSTRACT The cyclic-oligonucleotide-based antiphage signaling system (CBASS) is essential for bacterial defense against phage infections, mirroring many features of the eukaryotic cGAS-STING pathway. Although metal ions are well-known regulators of cGAS-STING activation, their impact on CBASS-mediated antiviral function remains largely unexplored. Here, we show that manganese (Mn 2+ ) serves as a key cofactor to enhance CBASS activation. Upon phage infection, the intracellular Mn 2+ level is elevated, and the gene expression of the Mn 2+ transportation system is upregulated. We found that Mn 2+ directly augments the activity of DncV, markedly boosting 3′3′-cGAMP production. Consequently, the phospholipase CapV is activated more rapidly, driving premature bacterial cell lysis and curtailing phage replication. Notably, Mn 2+ also alleviates folate-mediated inhibition of DncV, underscoring its role as a potent modulator of cyclic dinucleotide signaling. Our findings reveal a mechanism through which Mn 2+ confers bacterial resistance to phages, mirroring the Mn 2+ -enhanced antiviral responses of mammalian cGAS-STING. IMPORTANCE Bacteriophages pose a persistent threat to bacterial survival, driving the evolution of diverse antiviral systems, including the cyclic-oligonucleotide-based antiphage signaling system (CBASS) immunity. Here, we reveal that manganese (Mn 2+ ) acts as a pivotal cofactor for CBASS, directly enhancing the activity of the cGAS-like cyclase DncV to generate 3′3′-cGAMP, which, in turn, activates the phospholipase CapV. This Mn 2+ -driven DncV activation induces rapid bacterial cell death, thereby limiting phage replication. These findings underscore a striking parallel with mammalian cGAS-STING, where Mn 2+ likewise amplifies antiviral responses. By illuminating the importance of Mn 2+ homeostasis in bacterial phage resistance, our study broadens the understanding of bacterial innate immunity and highlights a deeply conserved mechanism across prokaryotes and eukaryotes.