1. Virus so small they can be seen only with the aid of a powerful electron microscope. simplest viruses contain only a few genes, whereas the most complex may have more than a hundred genes Most viruses infect only a very specific kind of cell. viruses that infect bacteria are called bacteriophages. Latin for poison!
3. Glycoproteins Receptor molecules on the outside of the virus. Proteins and carbohydrates attached. Used for recognition on the cell membrane or cell wall.
4. Lytic cycle In a lytic infection, a virus enters a bacterial cell, makes copies of itself, and causes the cell to burst, or lyse. Bacteriophage T4 is an example of a bacteriophage that causes such an infection. The host cell lyses, releasing hundreds of virus particles that go on to infect other cells.
5. Provirus The virus that has become part of the DNA of the host cell. also called a prophage.
6. Lysogenic In a lysogenic infection a host cell is not immediately taken over. The viral DNA is then copied along with the host DNA without damaging the host. Viral DNA multiplies as the host cells multiply. In this way, each generation of daughter cells derived from the original host cell is infected. Bacteriophage DNA that becomes embedded in the bacterial hosts DNA is called a prophage. Influences from the environmentradiation, heat, etctrigger the prophage to become active.
7. Prions Miss folded proteins Cause disease No nucleic acid involved! Mad Cow disease is an example prions, short for protein infectious particles. Prions are misfolded proteins in the brain that cause a chain reaction of misfolding in other normal proteins they contact, eventually clogging the brain tissue and causing disease Many animals, including humans, can become infected with prions
8. Viroids Small RNA segments Cause disease in plants Possibly can infect animals
9. Pili Attachment structures Also used for reproduction