No evidence of inhibition of horizontal gene transfer by CRISPR-Cas on evolutionary timescales.
No evidence of inhibition of horizontal gene transfer by CRISPR-Cas on evolutionary timescales.
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DOI：
10.1038/ismej.2015.20
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发表时间：
2015-09
期刊：
影响因子：
--
通讯作者：
Koonin EV
中科院分区：
文献类型：
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作者：
Gophna U;Kristensen DM;Wolf YI;Popa O;Drevet C;Koonin EV
古细菌和细菌的CRISPR（成簇、规则、间隔、短、回文重复序列）-Cas（CRISPR相关基因）系统提供了针对病毒和其他自私元素的适应性免疫，并被认为可以减少水平基因转移（HGT）。限制新遗传物质的获得可能是CRISPR-Cas维持的适应性成本的来源之一，也是CRISPR-Cas在细菌和环境中不均匀分布的原因之一。我们试图检验微生物中CRISPR-Cas的活性与最近HGT的程度呈负相关的假设。使用HGT的三个独立测量，我们发现CRISPR阵列的长度（反映免疫系统的活性）与最近HGT事件的估计数量之间没有显著的依赖性。与此相反，我们观察到一个显着的负相关性之间的估计程度的HGT和微生物的生长温度，这可以解释较低的遗传多样性在较热的环境。我们假设，CRISPR-Cas系统似乎对移动的元素的抗性和HGT倾向的进化中的相关事件发生在种群规模上，而不是在物种进化的时间尺度上。
The CRISPR (clustered, regularly, interspaced, short, palindromic repeats)–Cas (CRISPR-associated genes) systems of archaea and bacteria provide adaptive immunity against viruses and other selfish elements and are believed to curtail horizontal gene transfer (HGT). Limiting acquisition of new genetic material could be one of the sources of the fitness cost of CRISPR–Cas maintenance and one of the causes of the patchy distribution of CRISPR–Cas among bacteria, and across environments. We sought to test the hypothesis that the activity of CRISPR–Cas in microbes is negatively correlated with the extent of recent HGT. Using three independent measures of HGT, we found no significant dependence between the length of CRISPR arrays, which reflects the activity of the immune system, and the estimated number of recent HGT events. In contrast, we observed a significant negative dependence between the estimated extent of HGT and growth temperature of microbes, which could be explained by the lower genetic diversity in hotter environments. We hypothesize that the relevant events in the evolution of resistance to mobile elements and proclivity for HGT, to which CRISPR–Cas systems seem to substantially contribute, occur on the population scale rather than on the timescale of species evolution.