Obelisks

Newfound ‘obelisks’ join viruses, viroids as third unusual life form

• They are circular bits of genetic material that contain one or two genes and self-organise into a rod-like shape.
• Like viroids, obelisks have a circular single-stranded RNA genome and no protein coat but, like viruses, their genomes contain genes that are predicted to code for proteins.
• All obelisks so far described encode a single major protein known as obulin, and many encode a second, smaller obulin.
• Obelisks probably rely on microbial host cells to replicate, including those that live inside humans to replicate.
• Bacteria or fungi are likely hosts, but it is not known which exact species harbour these elements.