Viruses

• Non-cellular and non-living, smallest known microbe (about 1 millionth of an mm long); so cannot be seen with a light microscope only an electron microscope, often look crystalline in structure
• They do not have a cytoplasm, cell membrane, cell wall or nucleus, virus particles are called virions and come in a variety of shapes: polyhedral, spherical helical, and complex
• Virus examples - Tobacco Mosaic, Adenovirus, Influenza, and Bacteriophage
• All viruses are pathogenic (if it infects you, you get sick) parasites that must live inside another cell (a host), some viruses have a latent infection; host cell has to trigger viral replication