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首页> 外文期刊>Journal of bacteriology >Defense Islands in Bacterial and Archaeal Genomes and Prediction of Novel Defense Systems
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Defense Islands in Bacterial and Archaeal Genomes and Prediction of Novel Defense Systems

机译：细菌和古细菌基因组中的防御岛和新型防御系统的预测

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The arms race between cellular life forms and viruses is a major driving force of evolution. A substantial fraction of bacterial and archaeal genomes is dedicated to antivirus defense. We analyzed the distribution of defense genes and typical mobilome components (such as viral and transposon genes) in bacterial and archaeal genomes and demonstrated statistically significant clustering of antivirus defense systems and mobile genes and elements in genomic islands. The defense islands are enriched in putative operons and contain numerous overrepresented gene families. A detailed sequence analysis of the proteins encoded by genes in these families shows that many of them are diverged variants of known defense system components, whereas others show features, such as characteristic operonic organization, that are suggestive of novel defense systems. Thus, genomic islands provide abundant material for the experimental study of bacterial and archaeal antivirus defense. Except for the CRISPR-Cas systems, different classes of defense systems, in particular toxin-antitoxin and restriction-modification systems, show nonrandom clustering in defense islands. It remains unclear to what extent these associations reflect functional cooperation between different defense systems and to what extent the islands are genomic “sinks” that accumulate diverse nonessential genes, particularly those acquired via horizontal gene transfer. The characteristics of defense islands resemble those of mobilome islands. Defense and mobilome genes are nonrandomly associated in islands, suggesting nonadaptive evolution of the islands via a preferential attachment-like mechanism underpinned by the addictive properties of defense systems such as toxins-antitoxins and an important role of horizontal mobility in the evolution of these islands.
机译：细胞生命形式与病毒之间的军备竞赛是进化的主要动力。细菌和古细菌基因组的很大一部分致力于抗病毒防御。我们分析了细菌和古细菌基因组中防御基因和典型动素组成分（例如病毒和转座子基因）的分布，并证明了在基因组岛上抗病毒防御系统以及移动基因和元件具有统计学意义的聚类。防御岛上富含假定的操纵子，并包含许多超额代表的基因家族。对这些家族中基因编码的蛋白质进行的详细序列分析表明，它们中的许多是已知防御系统组件的不同变体，而另一些则显示出暗示新型防御系统的特征，例如特征性操纵子组织。因此，基因组岛为细菌和古细菌抗病毒防御的实验研究提供了丰富的材料。除了CRISPR-Cas系统外，不同类型的防御系统，特别是毒素-抗毒素和限制性修饰系统，在防御岛上显示出非随机聚集。目前尚不清楚这些关联在多大程度上反映了不同防御系统之间的功能合作，以及这些岛屿在多大程度上积累了多种非必需基因，特别是通过水平基因转移获得的非必需基因的基因组“汇”。防御岛的特征类似于动车岛的特征。防御和动植物基因在岛屿上是非随机相关的，这表明岛屿通过一种优先的依附类机制进行非适应性进化，这种机制受防御系统的有毒特性（如毒素-抗毒素）的支持，并在这些岛屿的进化中具有水平移动性的重要作用。

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