Core Viewpoint - The article discusses the discovery of the cyclic-oligonucleotide-based anti-phage signaling systems (CBASS) in bacteria, highlighting its role in bacterial immunity against phage infections and the molecular mechanisms involved in the activation of phospholipase effectors [1][2][9]. Group 1: CBASS System Overview - The CBASS system is a complex defense mechanism found in over 10% of bacteria and archaea, which activates in response to phage infections by synthesizing cyclic oligonucleotide second messengers [1]. - This system has a clear evolutionary homology with the cGAS-STING immune pathway in higher organisms, indicating a shared evolutionary origin [1]. Group 2: Research Findings - A study published in the journal Cell reveals that phospholipase effectors in the CBASS system self-assemble into supramolecular fiber structures upon responding to cyclic oligonucleotide molecules, leading to bacterial cell membrane degradation and cell death [2][9]. - The research identifies that in its inactive state, the phospholipase effector CapE exists as a dimer with a closed substrate channel, which opens upon binding with the cyclic oligonucleotide cUA, triggering a conformational change and self-assembly into fibrous structures [5][6]. Group 3: Mechanism of Action - The activated CapE can efficiently cleave the cell membrane, resulting in cell lysis and death, demonstrating a conserved mechanism among CBASS phospholipase effectors [6][9]. - Similar phospholipase effectors, such as CapV from Vibrio cholerae, also form fibrous structures upon binding with second messenger molecules, suggesting a common mechanism for executing cell-killing functions [6][7]. Group 4: Evolutionary Insights - The self-assembly of phospholipase effectors in response to cyclic oligonucleotides mirrors the polymerization observed in the cGAS-STING pathway in eukaryotic cells, indicating a parallel evolution in immune response strategies between bacteria and higher organisms [7][9].