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首页> 外文期刊>Philosophical Transactions of the Royal Society of London, Series B. Biological Sciences >Different genetic and morphological outcomes for phages targeted by single or multiple CRISPR-Cas spacers
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Different genetic and morphological outcomes for phages targeted by single or multiple CRISPR-Cas spacers

机译：由单或多个CRISPR-CAS间隔物针对的噬菌体不同的遗传和形态结果

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摘要

CRISPR-Cas systems provide bacteria and archaea with adaptive immunity against genetic invaders, such as bacteriophages. The systems integrate short sequences from the phage genome into the bacterial CRISPR array. These 'spacers' provide sequence-specific immunity but drive natural selection of evolved phage mutants that escape the CRISPR-Cas defence. Spacer acquisition occurs by either naive or primed adaptation. Naive adaptation typically results in the incorporation of a single spacer. By contrast, priming is a positive feedback loop that often results in acquisition of multiple spacers, which occurs when a pre-existing spacer matches the invading phage. We predicted that single and multiple spacers, representative of naive and primed adaptation, respectively, would cause differing outcomes after phage infection. We investigated the response of two phages, phi TE and phi M1, to the Pectobacterium atrosepticum type I-F CRISPR-Cas system and observed that escape from single spacers typically occurred via point mutations. Alternatively, phages escaped multiple spacers through deletions, which can occur in genes encoding structural proteins. Cryo-EM analysis of the phi TE structure revealed shortened tails in escape mutants with tape measure protein deletions. We conclude that CRISPR-Cas systems can drive phage genetic diversity, altering morphology and fitness, through selective pressures arising from naive and primed acquisition events.
机译：CRISPR-CAS系统为细菌和古痤疮提供适应性免疫的遗传入侵者，例如噬菌体。该系统将短序列与噬菌体基因组相容到细菌CRISPR阵列中。这些“垫片”提供序列特异性免疫，但驱动自然选择的进化噬菌体突变体，逃离CRISPR-CAS防御。间隔采集通过天真或初步的适应来发生。天真的适应通常导致掺入单个间隔物。相反，引发是一种正反馈回路，其经常导致采集多个间隔物，当预先存在的间隔符匹配入侵噬菌体时发生这种情况。我们预测，单一和多个间隔物，分别代表幼稚和灌注的适应性，将在噬菌体感染后导致不同的结果。我们研究了两种噬菌体，phi te和phi m1的响应，对胶杆菌患有I-f CISPR-CAS系统，并且观察到从单个间隔物逸出，通常通过点突变发生。或者，噬菌体通过缺失逃离多个间隔物，其可以在编码结构蛋白的基​​因中发生。 PHI TE结构的冷冻EM分析显示逃生突变体中的缩短斑块蛋白质缺失。我们得出结论，CASPR-CAS系统可以通过Naive和Primed获取事件产生的选择性压力来推动噬菌体遗传多样性，改变形态和健康。

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