Viruses and Prokaryotes

1. Viruses and Prokaryotes Chapter 20 pages 572 - 599

2. Estimated number of viruses on the planet is 1031! If you stacked them up you would make a tower that would stretch beyond our galaxy and its neighbors. Every time you get sick with the flu the number of viruses in your body rises to 100 trillion in a few days. The slide shows viral abundance in the oceans

3. Virus – a non-living particle made primarily of proteins and nucleic acids. They can reproduce only by infecting cells. Bacteriophage –attacks bacteria Influenza virus

4. Lytic infection – viral DNA enters cell, makes copies of itself and causes the cell to burst (lyse)Lysogenic infection – viral DNA becomes part of host DNA (prophage) and may not become active for many generations

5. Shingles is a viral disease caused by the virus that causes chicken pox. After recovery from chicken pox the virus lies dormant in the cells, sometimes for years, before causing its next disease, Shingles.

7. Chicken pox – highly contagious viral disease. Causes raw pockmarks that heal. The disease is uncommon now with the advent of the vaccine.

8. Common cold is a viral disease of the upper respiratory tract. It is a retrovirus in that it contains RNA, not DNA. The host cells ribosomes translate the viral RNA into capsid and other viral proteins. Within 8 hours the host cell releases hundreds of new viruses to attack other cells.

9. HIV is a retrovirus that causes AIDS. When this virus infects a cell it makes a DNA copy of its RNA which is inserted into the host cell DNA. Like a prophage it may not activate for a while. When it does it programs the cell to produce viral proteins and RNA.

10. The HIV virus attacks T4 helper cells. These are white blood cells that help acitivate other immune cells when the body is attacked by disease. • HIV infection sequence

11. Prokaryotes are either Archaea or Eubacteria. Eubacteria are the larger of the two domains.

12. Eubacteria cell structure. Gram negative bacteria do not stain well and are more resistant to antibiotics. Gram negative bacteria Gram positive with negative

13. Archaebacteria cell structure is more similar to Eukaryotes than to Eubacteria. Archaebacteria lack peptidoglycan in their cell wall.

14. Bacteria are classified according to cell shape.

15. Bacterial colony shapes.

16. Various bacteria colony shapes and colors

17. Hallophile bacteria colonies. Pink color is the dominant trait. Needs extremely salty environment to live.

18. How organisms get energy

19. Binary Fission – A form of asexual reproduction. Under favorable conditions bacteria can reproduce every 20 min.

20. Endospore formation – in poor conditions many bacteria can form an endospore. These spores have a tough outer coat that resists stains. The spores can exist for years and “come alive” when conditions are favorable for growth.

21. Bacterial conjugation – a hollow bridge forms between two cells and and exchange of genetic material, a plasmid, occurs. This results in a cell with a different genetic genotype.

22. Obligate aerobe bacteria. These bacteria need oxygen to survive. An example would be Mycobacterium tuberculosis: the bacterium that causes tuberculosis in human beings.

23. Obligate anaerobe. These bacteria die in the presence of oxygen. they live deep in the soil, animal intestines or airtight containers. An example is Clostridium botulinum; the bacterium that causes botulism

24. A nerve toxin that the bacterium emits is what causes the disease. One of the initial symptoms is droopy eyelids.

25. Facultative anaerobe – this type of bacteria can survive without oxygen when necessary. Esherichia Coli lives anerobically in sewage and anaerobically in human intestines.

26. Bacteria are essential in the decomposition of of organic matter. In this way they return needed raw materials back into the environment. They are especially useful in the decomposition of sewage.

27. A compost pile is a way that people use bacteria to decompose organic material

28. Producers – photosynthetic bacteria are important producers. The cyanobacteriumProchlorococcusis probably the most abundant photosynthetic organism on the planet.

29. Prochlorococcus distribution.

30. Anabena – fresh water cyanobacteria – the heterocysts are cells that specialize in nitrogen fixation. Akinetes are spore-like cells that function in reproduction

31. Nitrogen fixation. Nitrogen is needed to make proteins and other molecules. Only a few prokaryotes can convert N2 into useful forms. The process involves turning N2into ammonia and the ammonia into nitrates that plants can use or attached to amino acids that all organisms can use

32. Disease causing bacteria (pathogens) cause disease by destroying living cells or by releasing chemicals that upset homeostasis. The slide below shows a person with strep throat.

33. Releasing Toxins – Some bacteria cause disease because of a particular deadly toxin they release. Diptheria is an upper respiratory illness caused by a bacterium that releases a toxin

34. Meningococcal disease – the bacteria attack the lining of the brain and the endotoxin they produce can affect the heart and rupture blood vessels.

35. A person with meningococcal disease. Even with prompt antibiotic treatment 10% of infected people die.

36. The endotoxins rupturing of blood vessels can result in amputation. Even when antibiotics are used early about 10% of the cases will be fatal.

37. Controlling bacteria – Washing hands and surfaces with soap. Soap does not kill the bacteria but it is washed away.

38. Disinfectants – Chemical solutions (bleach, ammonia, hydrogen peroxide) can be used to to clean surfaces

39. Food storage – refrigeration, canning, pickling, salting, dehydration can make it difficult for bacteria to grow

40. Sterilization by heat. Objects can be sterilized when placed boiling water

41. Vaccines – A vaccine is a heat killed pathogen or part of a pathogen. The body responds to the presence of the foreign protein by making antibodies against the heat killed pathogen. If a live pathogen shows up the antibodies are already there and the pathogen is defeated before it has a chance to start.

44. Polio Vaccine – Developed by Dr. Jonas Salk in 1952. This vaccine effectively ended the incidence of polio in the US.

45. A small percentage of people who contracted polio would become paralyzed as the virus attacked the motor nerves. These patients are in iron lungs as their chest muscles have become paralyzed.

46. Franklin D. Roosevelt contracted polio as a young man. He was loathe to let the public see him in a wheel chair. This one of the few photos that exist of him sitting in a wheel chair

47. Jack Nicklaus had polio as a young boy. Fortunately it did not cause any paralysis. Only .5% of people infected would develop a paralytic symptoms. But among millions infected this ended up to be a lot of people.

48. Sister Kenny – a self taught Australian nurse developed a physical therapy for polio victims that greatly reduced their chances of becoming paralyzed. She founded and ran the Sister Kenny institute for many years.

49. Viral diseases do not respond to antibiotics, but some can be prevented with vaccines. There are some new medications out that attack specific viral enzymes that host cells do not have.

50. Campaign to eradicate Polio. Global effort begun in 1988 by WHO – World Health Organization. Cases have been reduced by 99.9% (From hundreds of thousands to 291 in 2012). This child is getting the oral vaccine which contains a weakened virus.