Viroid-like colonists of human microbiomes
Highlights
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Obelisks are a phylogenetically distinct group of microbiome-associated, viroid-like RNAs
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Found globally in diverse niches, obelisks also occur in human stool and oral microbiomes
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The human oral bacterium Streptococcus sanguinis SK36 harbors a distinct “obelisk-S.s”
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Under replete growth conditions, obelisk-S.s appears to be disposable for SK36 growth
Summary
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.
Read more at:
https://www.cell.com/cell/abstract/S0092-8674(24)01091-2?dgcid=raven_jbs_aip_email
