The nature of viruses Viruses contain one kind of nucleic acid (dNa or RNa genome) inside a protein shell (capsid), which may be surrounded by a lipid bilayer membrane(envelope). The resulting complete virus particle s called a virion Membrane Matrix prote Nucleocapsid Capsid (icosahedral) ource: Ryan K), Ray CG: Sherris Medical Microbiology, Sth Edition: Copyright o The McGraw-Hill Companies, Inc. All rights reserved.The Nature of Viruses ¾ Viruses Viruses contain contain one kind of nucleic nucleic acid (DNA or RNA genome) inside a protein shell (capsid), which may be surrounded by a lipid bila yer membrane (envelo p e). The resultin g com plete virus particle is called a virion