Unexpectedly high mutation rate of a deep-sea hyperthermophilic anaerobic archaeon
Unexpectedly high mutation rate of a deep-sea hyperthermophilic anaerobic archaeon
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DOI：
10.1038/s41396-020-00888-5
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发表时间：
2021-01-15
期刊：
影响因子：
11
通讯作者：
Luo, Haiwei
中科院分区：
文献类型：
--
作者：
Gu, Jiahao;Wang, Xiaojun;Luo, Haiwei
深海热液喷口类似于早期地球，因此占主导地位的热球菌科居民，在古菌树的进化上占据基础地位，并采取专性厌氧、超嗜热的自由生活生活方式，可能是研究早期生命进化的绝佳模型。在这里，我们确定了代表性物种广热热球菌的无偏突变率超过所有已知的自由生活原核生物1-2个数量级，从而拒绝了长期以来的假说，即超嗜热菌选择性地偏爱低突变率。我们进一步对该物种的多个不同分离株进行了测序，并计算出T. eury Thermalis的有效种群规模比其他自由生活的原核生物低1-2个数量级。这些数据共同表明，该物种的高突变率不是选择性偏爱的，而是由随机遗传漂变驱动的。这些不寻常数据的可用性还有助于探索微生物基因组大小进化的机制。我们发现，基因组大小与突变率呈负相关，与 30 个细菌和古菌谱系的有效种群大小呈正相关，这表明突变率增加和随机遗传漂变可能是驱动微生物基因组减少的两个重要机制。未来确定基因组高度减少的更具代表性谱系的无偏突变率，例如在海洋微生物群落中占主导地位的原绿球藻和海洋细菌，对于检验这些假设至关重要。
Deep-sea hydrothermal vents resemble the early Earth, and thus the dominant Thermococcaceae inhabitants, which occupy an evolutionarily basal position of the archaeal tree and take an obligate anaerobic hyperthermophilic free-living lifestyle, are likely excellent models to study the evolution of early life. Here, we determined that unbiased mutation rate of a representative species, Thermococcus eurythermalis, exceeded that of all known free-living prokaryotes by 1-2 orders of magnitude, and thus rejected the long-standing hypothesis that low mutation rates were selectively favored in hyperthermophiles. We further sequenced multiple and diverse isolates of this species and calculated that T. eurythermalis has a lower effective population size than other free-living prokaryotes by 1-2 orders of magnitude. These data collectively indicate that the high mutation rate of this species is not selectively favored but instead driven by random genetic drift. The availability of these unusual data also helps explore mechanisms underlying microbial genome size evolution. We showed that genome size is negatively correlated with mutation rate and positively correlated with effective population size across 30 bacterial and archaeal lineages, suggesting that increased mutation rate and random genetic drift are likely two important mechanisms driving microbial genome reduction. Future determinations of the unbiased mutation rate of more representative lineages with highly reduced genomes such as Prochlorococcus and Pelagibacterales that dominate marine microbial communities are essential to test these hypotheses.