1. Bacteria and Viruses Chapter 19

2.  I can identify the two bacteria kingdoms.  I can describe the characteristics of the two kingdoms.  I can describe how bacteria are identified.  I can describe the ways in which bacteria obtain and use energy.

3. Introduction  Prokaryotic cells lack a nucleus and are much smaller than plant and animal cells.  Remember, prokaryotic cells are single celled organisms.  Prokaryotes are often referred to as bacteria.

4. Introduction  Prokaryotes can be divided into two kingdoms: eubacteria and archaebacteria.  The eubacteria is the larger of the two kingdoms and live almost everywhere.  Eubacteria are surrounded by a cell wall.  The cell wall of eubacteria has a carbohydrate called peptidoglycan.

5. Introduction  Archaebacteria lack peptidoglycan and have different cell membrane lipids.  The DNA sequences of archaebacteria are more like plant and animal cells than eubacteria.  Scientists think archaebacteria are the ancestors of eukaryotes (cells with a nucleus).

6. Identifying Prokaryotes  Prokaryotes are identified by their shapes, the chemicals in their cell wall, the ways they move, and the ways they obtain energy.

7. Shapes  Bacteria come in three shapes: rod-shaped, spherical, and spiral shaped.  Bacteria can form long chains or large clusters.

8. Staining  A special staining technique called Gram staining can differentiate between the two types of cell walls.  Gram positive bacteria look purple under a microscope.  Gram positive bacteria are eubacteria and contain peptidoglycan in their cell walls.

9. Staining  Gram negative bacteria look pink under a microscope.  Gram negative bacteria are archaebacteria and lack peptidoglycan in their cell walls.

10. Movement  Bacteria can be identified by how they move as well.  Some bacteria have flagella, which is a whip-like structure used for movement.  Some bacteria lash, snake, or spiral forward.

11. Movement  Some glide in a layer of slime- like material.  However, many prokaryotes do not move at all.

12. Energy  Prokaryotes have diverse adaptations that allow them to live in nearly every environment imaginable.  Photoautotrophs are prokaryotes that carry out photosynthesis similar to green plants.  The photoautotrophs are found where light is abundant.

13. Energy  Chemoautotrophs obtain energy from inorganic molecules like ammonia, nitrites, sulfur, iron, or hydrogen sulfide gas.  Most prokaryotes are heterotrophs and get energy from organic molecules.

14. Energy  There is also a group of bacteria that is both autotrophic and heterotrophic.  Photoheterotrophs capture sunlight for energy but need organic compounds for nutrition from other organisms.

15. Energy  Bacteria need a constant supply of energy.  Energy is released through cellular respiration and fermentation.  Cellular respiration requires oxygen and fermentation does not.

16. Energy  Organisms that require a constant supply of oxygen are called obligate aerobes.  Some bacteria do not require oxygen at all and are actually poisoned by oxygen.  Bacteria that must live without oxygen are called obligate anaerobes.

17. Energy  Facultative anaerobes can survive with or without oxygen.  They can switch between cellular respiration and fermentation and can live almost anywhere.

18. Reproduction  Prokaryotes can reproduce at astonishing rates if they have enough nutrients available.  Prokaryotes use asexual reproduction, which means they are single parents.

19. Reproduction  When a prokaryote grows to nearly double its size it replicates its DNA, splits in half, and produces two identical cells.  This process is known as binary fission.

20. Reproduction  Even though most bacteria reproduce using binary fission, some can transfer genetic material from one cell to another.  This exchange is called conjugation.

21. Reproduction  During conjugation, a hollow bridge forms between two cells and genes move from one cell to another.  Conjugation increases genetic diversity in prokaryotes.

22. Bacteria in Nature

23.  I can explain the role bacteria play in nature as decomposers.  I can explain the role bacteria play in recycling nitrogen.  I can explain what a pathogen is.  I can explain why sterilization is important.  I can explain where the DNA in mitochondria and chloroplasts evolved from.

24. Bacteria in Nature  Bacteria are vital to the living world.  They can be found living almost anywhere.

25. Decomposers  Bacteria can be decomposers.  Decomposers help the ecosystem recycle nutrients by breaking down dead matter into simpler substances.

26. Decomposers  Bacteria also play a crucial role in treating sewage, which contains human waste, discarded food, garbage, and chemical waste.  Bacteria break down complex compounds into simpler ones.

27. Decomposers  This process produces purified water, nitrogen, and carbon dioxide.

28. Nitrogen Fixers  Plants and animals depend on bacteria for nitrogen.  Nitrogen is required to make amino acids for proteins.  Even though our atmosphere is 78% nitrogen, nitrogen gas cannot be used directly by plants and animals.

29. Nitrogen Fixers  Certain bacteria can convert nitrogen gas into useable forms through nitrogen fixation.  Soybeans have a mutualistic relationship with a nitrogen fixing bacteria.  The bacteria converts nitrogen into a useable form and the plant provides nutrients for the bacteria.

30. Pathogens  Some bacteria are pathogens.  A pathogen is a disease causing agent.

31. Pathogens  Bacteria causes disease in one of two ways.  Damage the organism’s tissues by breaking them down for food.  Release toxins that harm the body.

32. Pathogens  Many bacterial diseases can be prevented by vaccines.  Bacterial infections can also be treated with antibiotics, like penicillin.  Antibiotics are compounds that block the growth and reproduction of bacteria.

33. Controlling Bacteria  Sterilization is used to destroy bacteria by using high heat or chemicals.  Most bacteria cannot survive high temperatures for long and can be killed in boiling water.  Disinfectants also kill bacteria.

34. Controlling Bacteria  Refrigeration stops/slows bacteria from spoiling food.  Boiling, frying, and steaming can sterilize foods because cooking temperatures are high enough to kill bacteria.  Food can be preserved for a long time by canning or adding salt, vinegar, or sugar.

35. Mitochondria and Chloroplasts  Two organelles found in cells are believed to be descendants of ancient prokaryotic cells.  Mitochondria and chloroplasts both contain their own DNA.  At some point in time, the prokaryote ancestors of these organelles merged with eukaryotic cells.

36. Mitochondria and Chloroplasts  Over time, the DNA of the cell nucleus took over more and more of the genetic information of each organelle.  The DNA in chloroplasts and mitochondria is the remnants of genetic information of the bacteria they descended from.

37. Viruses and Prions

38.  I can describe the structure of a virus.  I can explain why viruses are not living.  I can explain how a virus attacks a cell.  I can describe a prion.

39. Viruses  Viruses are particles of nucleic acid (DNA or RNA), proteins, and lipids that can only reproduce by infecting living cells.  It is important to note that viruses are not living things because they do not meet all the requirements or characteristics of life.

40. Viruses  Viruses cannot reproduce on their own, which is the main characteristic of life that is not met.  However, viruses do contain DNA and they do change over time.  A virus enters living cells, and they use the cell to make more viruses.

41. Viruses  A typical virus is composed of a core of DNA or RNA surrounded by a protein coat.  The outer protein coat is called a capsid.  The capsid contains proteins that trick a host cell into allowing a virus into the cell.

42. Viruses  Once inside, the viral genes take over the cell, and the cell becomes a factory for viruses.  Often, the host cell dies once the copies of the virus are made.  Most viruses can only infect specific cells. Plant viruses cannot infect animal cells.

43. Viruses  A bacteriophage is a virus that infects bacteria.  There are two types of ways a virus can attack a cell.

44. Lytic Infections a)Virus enters cell and injects DNA. b) The cell cannot differentiate between the viral DNA and its own DNA. c) The viral DNA takes over, shutting down the cell defenses. d) The host cell makes copies of the virus and the cell manufactures new viruses. e) The cell bursts or lyses and releases the new viruses.

45. Lysogenic Infections a) Virus enters cell and injects DNA. b) The virus DNA is embedded in the host cell. c) The viral DNA is replicated along with the host cell’s DNA indefinitely. d) The host cell does not die immediately.

46. Viruses  Viruses cause human diseases like polio, AIDS, measles, influenza, and rabies.  Most viral infections attack and destroy specific cells.  The destruction of specific cells causes symptoms of the disease.

47. Viruses  The best way to protect against most viral infections is prevention.  Most viral infections are prevented using vaccines.  A vaccine is a preparation of dead or weakened viruses that are injected into an organism.

48. Viruses  The injected vaccine activates the immune system to create antibodies.  Antibodies are activated when an organism is exposed to a disease causing agent.  Most vaccines are only effective if they are used prior to infection.

49. Prions  Disease causing particle made only of protein.  Contains no DNA or RNA, therefore, prions are not living organisms.  They are thought to cause mad cow disease.