Before revision: Nucleic acid-containing infectious agents Viruses Researchers initially described viruses as "poisons" or "toxins", then as "infectious proteins"; but they possess genetic material, a defined structure, and the ability to spontaneously assemble from their constituent parts.
After revision: alt=an image showing types of virus|179x179px|Types of virusNucleic acid-containing infectious agents Viruses Researchers initially described viruses as "poisons" or "toxins", then as "infectious proteins"; but they possess genetic material, a defined structure, and the ability to spontaneously assemble from their constituent parts.