Subviral particles are infectious entities smaller than viruses that, together with viruses, constitute the category of nonliving infectious agents — acellular, organelle-free, incapable of generating ATP or reproducing autonomously, and therefore obligately dependent on a host. The two recognized classes are viroids, consisting solely of a small circular RNA molecule with no capsid, thought to be catalytic (ribozymatic) RNA capable of self-cleavage to propagate, and prions ("proteinaceous infectious particles"), which contain no nucleic acid whatsoever and propagate by conformational templating, in which a misfolded β-sheet form of a protein converts the normal α-helical form of the same amino acid sequence, yielding accumulating protein deposits and consequent tissue destruction. This concept belongs to microbiology and infectious disease, and it extends the definition of an infectious agent beyond cellular life and beyond nucleic-acid-encoded information, thereby testing the boundary conditions of what counts as living and as heritable information.
Subviral particles are infectious entities smaller than viruses that, together with viruses, constitute the category of nonliving infectious agents — acellular, organelle-free, incapable of generatin…