CRISPR-Cas in Pseudomonas aeruginosa provides transient population-level immunity against high phage exposures
CRISPR-Cas in Pseudomonas aeruginosa provides transient population-level immunity against high phage exposures
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DOI：
10.1093/ismejo/wrad039
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发表时间：
2024-01-08
期刊：
影响因子：
11
通讯作者：
Meaden，Sean
中科院分区：
文献类型：
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作者：
Watson，Bridget N. J.;Capria，Loris;Meaden，Sean
原核生物适应性免疫系统CRISPR-Cas(群集规则间隔短回文重复序列；CRISPR相关)需要获得针对入侵的移动遗传元件(如噬菌体)的间隔区序列。以前的工作已经确定了驱动模式有机体铜绿假单胞菌PA14对其噬菌体DMS3vir的基于CRISPR的免疫进化的生态变量，导致噬菌体迅速灭绝。然而，目前尚不清楚这种获得性免疫在细菌群体中是否稳定，以及这种稳定程度如何取决于环境。在这里，我们研究了30天的进化实验中CRISPR间隔区的获得和丢失的动态，并确定了在长期维持免疫和支持噬菌体持久性的替代抗性策略的入侵之间打破平衡的条件。具体地说，我们发现，初始噬菌体剂量和再感染频率都决定了获得性CRISPR免疫是否长期保持，以及噬菌体能否与细菌共存。在群体遗传学水平上，CRISPR免疫的出现和丧失与高水平的间隔区多样性有关，而间隔区多样性随后由于携带菌毛相关突变的细菌的入侵而下降。总之，这些结果为CRISPR免疫获得和丧失的动态提供了高分辨率，并证明了累积噬菌体负荷决定了CRISPR在生态相关时间框架内的有效性。
The prokaryotic adaptive immune system, CRISPR-Cas (clustered regularly interspaced short palindromic repeats; CRISPR-associated), requires the acquisition of spacer sequences that target invading mobile genetic elements such as phages. Previous work has identified ecological variables that drive the evolution of CRISPR-based immunity of the model organismPseudomonas aeruginosaPA14 against its phage DMS3vir, resulting in rapid phage extinction. However, it is unclear if and how stable such acquired immunity is within bacterial populations, and how this depends on the environment. Here, we examine the dynamics of CRISPR spacer acquisition and loss over a 30-day evolution experiment and identify conditions that tip the balance between long-term maintenance of immunity versus invasion of alternative resistance strategies that support phage persistence. Specifically, we find that both the initial phage dose and reinfection frequencies determine whether or not acquired CRISPR immunity is maintained in the long term, and whether or not phage can coexist with the bacteria. At the population genetics level, emergence and loss of CRISPR immunity are associated with high levels of spacer diversity that subsequently decline due to invasion of bacteria carrying pilus-associated mutations. Together, these results provide high resolution of the dynamics of CRISPR immunity acquisition and loss and demonstrate that the cumulative phage burden determines the effectiveness of CRISPR over ecologically relevant timeframes.