Here, we describe “obelisks,” a class of heritable RNA elements sharing several properties: (1) apparently circular RNA ∼1 kb genome assemblies, (2) predicted rod-like genome-wide secondary structures, and (3) open reading frames encoding a novel “Oblin” protein superfamily. A subset of obelisks includes a variant hammerhead self-cleaving ribozyme. Obelisks form their own phylogenetic group without detectable similarity to known biological agents. Surveying globally, we identified 29,959 distinct obelisks (clustered at 90% sequence identity) from diverse ecological niches. Obelisks are prevalent in human microbiomes, with detection in ∼7% (29/440) and ∼50% (17/32) of queried stool and oral metatranscriptomes, respectively. We establish Streptococcus sanguinis as a cellular host of a specific obelisk and find that this obelisk’s maintenance is not essential for bacterial growth. Our observations identify obelisks as a class of diverse RNAs of yet-to-be-determined impact that have colonized and gone unnoticed in human and global microbiomes.

中文翻译：

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人类微生物组的类病毒样定植剂


在这里，我们描述了“方尖碑”，这是一类具有多种特性的可遗传 RNA 元件：（1） 明显的环状 RNA ∼1 kb 基因组组装，（2） 预测的杆状全基因组二级结构，以及 （3） 编码新的“Oblin”蛋白超家族的开放阅读框。方尖碑的一个子集包括一个变体的锤头自裂核酶。方尖碑形成自己的系统发育组，与已知的生物制剂没有可检测到的相似性。在全球范围内进行调查，我们从不同的生态位中确定了 29,959 个不同的方尖碑（以 90% 的序列同一性聚集）。方尖碑在人类微生物组中普遍存在，分别在查询的粪便和口腔宏转录组的 ∼7% （29/440） 和 ∼50% （17/32） 中检测到。我们将血链球菌确定为特定方尖碑的细胞宿主，发现该方尖碑的维护对于细菌生长不是必需的。我们的观察将方尖碑确定为一类具有尚未确定影响的不同 RNA，这些 RNA 已在人类和全球微生物组中定植且未被注意到。