Cactus plasmid analysis on Gabija and tmn

Bacterial defence against phage predation involves diverse immune systems acting both individually and concurrently, yet their interactions remain poorly understood. We investigated co-occurrence of 110 immune systems in 26,362 <i>Escherichia coli</i> genomes and identified numerous instances of co-occurrence and mutual exclusion. Co-occurrence of immune systems does not strongly correlate with co-localisation in the genome, and thus does not seem to be caused primarily by concurrent horizontal gene transfer. For several co-occurring pairs, we demonstrate synergistic anti-phage activity <i>in vivo</i>, with tmn synergising with immune systems containing sensory switch ATPase domains. Pairs of mutually exclusive immune systems in <i>E. coli</i> co-occur in other taxa, with one pair showing synergy, suggesting that evolution of immune repertoires is shaped by selection for robust phage resistance rather than by negative epistasis. Our findings demonstrate compatibility and synergy between immune systems, allowing bacteria to adopt flexible strategies for phage defence, driven by unique environmental pressures.

细菌抵御噬菌体捕食的过程依赖于多种可独立或协同发挥作用的免疫防御系统，但其相互作用机制仍未得到充分阐明。本研究针对26362个大肠杆菌（Escherichia coli）基因组中的110种免疫防御系统的共现情况展开分析，鉴定出大量共现与互斥的实例。免疫防御系统的共现现象与基因组内的共定位并无显著关联，因此其主要成因似乎并非同步水平基因转移（horizontal gene transfer）。针对多组共现的免疫系统对，本研究在活体内（in vivo）证实了其协同抗噬菌体活性，其中tmn可与携带感应开关ATP酶结构域的免疫系统发挥协同作用。在大肠杆菌中存在互斥关系的免疫系统对，在其他生物类群中也存在共现现象，其中一组免疫系统对还表现出协同活性，这表明细菌免疫组库的演化是由对高效噬菌体抗性的选择压力所塑造，而非负上位性（negative epistasis）效应。本研究结果证实了不同免疫系统间的兼容性与协同性，表明细菌可依托独特的环境压力驱动，形成灵活多样的噬菌体防御策略。