1. Viruses and Prokaryotes Chapter 20.1-20.3

2. Difference between Bacteria and Viruses A virus is a strand of DNA or RNA surrounded by a protein coat (CAPSID) Viruses are not considered to be alive!! Bacteria are one-celled microorganisms BOTH ARE INFECTIOUS! Any disease-causing agent is known as a PATHOGEN

3. Viral Structure Structure: genetic material surrounded by a capsid (protein shell). Different shapes and sizes Capsids surrounded by lipid envelope or protective outer coat

4. Why aren’t Viruses Alive? CAN ONLY REPRODUCE BY INFECTING OTHER LIVING CELLS

5. How do viruses enter cells? Viruses enter host cells in various ways Eukaryotic viruses fuse with host cell membrane Eukaryotic viruses enter through endocytosis When virus is taken in through endocytosis, the virus is now able to reproduce.

7. Lytic Infection Viruses cause two types of infections: First Type: LYTIC: causes host cell to burst, or lyse host bacterium The bacterophage attaches and injects it DNA into a host bacterium. The host bacterium breaks apart, or lyses. Bacteriophages are able to infect new host cells. The viral DNA directs the host cell to produce new viral parts. The parts assemble into new bacteriophages. The viral DNA forms a circle.

8. Lysogenic Infection Second Type: LYSOGENIC: does no immediate harm Prophage: phage DNA that is inserted into host cell DNA The viral DNA is called a prophage when it combines with the host cell’s DNA. Although the prophage is not active, it replicates along with the host cell’s DNA. Many cell divisions produce a colony of bacteria infected with prophage. The prophage may leave the host’s DNA and enter the lytic cycle.

9. Bacteriophages Viruses that infect bacteria ex: T-bacteriophage, which infects E. coli bacteria Pierce host cells and inject their DNA into viral hosts capsid DNA tail sheath tail fiber

10. Prokaryotes Unicellular organisms that lack a nucleus DNA not membrane bound and is located in cytoplasm Either ARCHAEA or BACTERIA

11. Bacteria Wall protection Flagella Peptidoglyclan cell wall (polymer of sugars and amino acids)

12. Archaea Walls lack peptidoglycan More like eukaryotes than bacteria genetically Live in extreme environments (salty, hot, methane-rich) Great Salt Lake

13. Prokaryote Structure and Function Prokaryotes vary in: Size Shape Mode of movement Way obtain and release energy

14. Size, Shape, and Movement Shapes: Bacilli, cocci, spirilla Bacilli: rod shape Cocci: spherical Spirilla: spiral, coiled

15. Energy Used by Prokaryotes: Nutrition & Metabolism Heterotroph: take in nutrients Photoheterotroph: use light energy and take in nutrients Photoautotroph: use light energy to convert carbon dioxide into carbon compounds Chemoautotroph: use energy released by chemical reactions to make food

16. Energy Released by Prokaryotes

17. Growth and Reproduction in Prokaryotes Reproduce by BINARY FISSION (asexual) When growth conditions are unfavorable, prokaryotic cells form an ENDOSPORE (thick, internal wall that encloses the DNA)

18. Recombination in Prokaryotes Mutations: cause prokaryotes to evolve Conjugation: exchange of genetic information when a hollow bridge forms between 2 bacterial cells and genetic material (plasmid) moves from one cell to the other.

19. Importance of Prokaryotes Decomposers Producers Nitrogen fixers Food production Drugs and antibiotics

20. What is a Pathogen? Microorganisms (viruses and bacteria) that cause disease

21. Bacterial Pathogens Bacteria cause disease by destroying living cells or by releasing chemicals that upset homeostasis Damage host tissue Release toxins Methods for controlling bacteria: removal, disinfectants, food storage and processing, sterilization by heat, vaccines, and antibiotics!

22. What is the Benefit of a Vaccine? Vaccines are made from weakened pathogens and stimulates the body’s OWN immune response Immune system gets MEMORY of pathogen Made from killed or weakened microbes or certain parts of microbes

23. Viral Diseases Viruses cause disease by directly destroying living cells or by affecting cellular processes in ways that upset homeostasis

24. Viral Diseases Some can be prevented with vaccines Examples of Viral Infections: Cold Influenza SARS HIV Mono Rabies Smallpox

25. Common Cold > 200 different viruses cause cold symptoms each season High mutation rate Symptoms last between 5-7 days

26. Influenza Why is the spread difficult to control? FLU virus Spreads quickly, causes local epidemics 20% of American population infected with flu virus per year Different types of flu viruses affect different species H1N1 (Swine Flu/Spanish Flu of 1918) Others infect pigs, birds, horses, etc.

27. SARS Severe Acute Respiratory Syndrome Coronavirus: cause respiratory or enteric infections 8096 infected and 774 deaths from 11/2002-7/2003 Symptoms: Fever, GI problems, cough, sore throat, shortness of breath

28. HIV/AIDS Human Immunodeficiency Virus Lysogenic and Lytic Infection Retrovirus: contain RNA and uses reverse transcriptase enzyme to make DNA (RNA  DNA) Viral DNA enters host nucleus and incorporates itself into host DNA strand and remains dormant for years When active, however, new viral parts are made, viruses bud or lyse through host cell and infect other host cells.

30. Mononucleosis Caused by Epstein-Barr Virus (EBV) Same family as the Herpes Virus Has a lytic and a latent cycle Increases WBCs in bloodstream Symptoms: severe fatigue, sore throat In US, 95% of adults 30-40 years old have antibodies against EBV

31. Rabies Causes acute encephalitis (swelling of the brain) Most commonly transmitted through bites from animals infected with the virus Virus travels to the brain via peripheral nerves Once symptoms begin to show (usually after a few months), the disease is usually fatal. IF BITTEN BY RABID ANIMAL: need 4 doses of Rabies Vaccine and 1 dose of Human Rabies Immunoglobulin

33. Smallpox Unique to humans Found in blood vessels of skin, throat, and mouth In 18th century, virus killed 400,000 Europeans; During 20th century, virus killed 300- 500 million people throughout the world Vaccine available As of NOW, Smallpox is the only infectious disease to be completely eradicated.

34. What is a Viroid? Infectious particle Cause disease in plants Passed through seeds or pollen Made only of single- stranded RNA

35. What is a Prion? ALSO Infectious Proteins that can cause other proteins to fold incorrectly Infections BUT contain NO GENETIC MATERIAL! Mad Cow Disease degeneration in the brain and spinal cord