Illustration of an RNA (ribonucleic acid) obelisk. RNA obelisks are viroid-like fragments of RNA that have been found replicating in bacteria in the human mouth and gut. They are formed of single-stranded circular RNA and have a rod-like secondary structure. The function of the proteins obelisks code for is not known. If they impact their bacterial hosts, it is possible that they could in turn impact human health.