CBASS (cyclic oligonucleotide-based antiphage signaling system) provides immunity against bacteriophage. The CD-NTase protein synthesizes cyclic nucleotides in response to infection; these serve as specific second messenger signals. The signals activate a diverse range of effectors, leading to bacterial cell death and thus abortive phage infection. A type I-B CBASS system (PubMed:32839535). Protects B.subtilis against phage infection. When IK1_05630 and IK1_05631 are introduced in B.subtilis BEST7003 there is 1000-fold protection against phage SBSphiC. Both genes are required for protection. Activation leads to bacterial cell lysis and death, which occurs before the phage has finished its replication cycle, thus protecting non-infected bacteria by aborting the phage infection and preventing its propagation. Part of the CBASS operon consisting of cdnD-IK1_05631.