Centre for Bacterial Resistance Biology, Imperial College London, London, UK.
Instituto de Biomedicina de Valencia (IBV), CSIC, Valencia, Spain.
Nat Commun. 2024 Aug 30;15(1):7539. doi: 10.1038/s41467-024-51915-4.
Many bacterial immune systems recognize phage structural components to activate antiviral responses, without inhibiting the function of the phage component. These systems can be encoded in specific chromosomal loci, known as defense islands, and in mobile genetic elements such as prophages and phage-inducible chromosomal islands (PICIs). Here, we identify a family of bacterial immune systems, named Tai (for 'tail assembly inhibition'), that is prevalent in PICIs, prophages and P4-like phage satellites. Tai systems protect their bacterial host population from other phages by blocking the tail assembly step, leading to the release of tailless phages incapable of infecting new hosts. To prevent autoimmunity, some Tai-positive phages have an associated counter-defense mechanism that is expressed during the phage lytic cycle and allows for tail formation. Interestingly, the Tai defense and counter-defense genes are organized in a non-contiguous operon, enabling their coordinated expression.
许多细菌免疫系统识别噬菌体结构成分以激活抗病毒反应，而不会抑制噬菌体成分的功能。这些系统可以编码在特定的染色体基因座中，称为防御岛，也可以编码在移动遗传元件中，如噬菌体和噬菌体诱导的染色体岛（PICIs）。在这里，我们鉴定了一类细菌免疫系统，命名为 Tai（代表“尾组装抑制”），它在 PICIs、噬菌体和 P4 样噬菌体卫星中普遍存在。Tai 系统通过阻止尾组装步骤来保护其细菌宿主群体免受其他噬菌体的侵害，导致释放无尾噬菌体，无法感染新宿主。为了防止自身免疫，一些 Tai 阳性噬菌体具有相关的防御机制，在噬菌体裂解周期中表达，允许形成尾部。有趣的是，Tai 防御和防御机制基因组织在一个不连续的操纵子中，使它们能够协调表达。
