Small subunit ribosomal RNA (SSU rRNA) genes, 16S in bacteria and 18S in eukaryotes, have been the standard phylogenetic markers used to characterize microbial diversity and evolution for decades. However, the reference databases of full-length SSU rRNA gene sequences are skewed to well-studied ecosystems and subject to primer bias and chimerism, which results in an incomplete view of the diversity present in a sample. We combine poly(A)-tailing and reverse transcription of SSU rRNA molecules with synthetic long-read sequencing to generate high-quality, full-length SSU rRNA sequences, without primer bias, at high throughput. We apply our approach to samples from seven different ecosystems and obtain more than a million SSU rRNA sequences from all domains of life, with an estimated raw error rate of 0.17%. We observe a large proportion of novel diversity, including several deeply branching phylum-level lineages putatively related to the Asgard Archaea. Our approach will enable expansion of the SSU rRNA reference databases by orders of magnitude, and contribute to a comprehensive census of the tree of life.

中文翻译：

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检索百万个高质量，全长的微生物16S和18S rRNA基因序列，而无需引物偏向。

细菌中的16S和真核生物中的18S是小的亚基核糖体RNA（SSU rRNA）基因，几十年来一直是表征微生物多样性和进化的标准系统发育标记。但是，全长SSU rRNA基因序列的参考数据库偏向经过深入研究的生态系统，并且容易受到引物偏倚和嵌合现象的影响，这导致无法完全了解样品中存在的多样性。我们将poly（A）-tail和SSU rRNA分子的反转录与合成的长读测序结合在一起，以高通量产生高质量，全长的SSU rRNA序列，而无需引物偏向。我们将我们的方法应用于来自七个不同生态系统的样本，并从生命的所有域中获得超过一百万个SSU rRNA序列，估计原始错误率为0.17％。我们观察到很大一部分新颖的多样性，包括几个与Asgard古细菌有关的深分支的门脉谱系。我们的方法将使SSU rRNA参考数据库的数量级扩展，并有助于对生命树进行全面普查。