19 Bacteria And Viruses


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19 Bacteria And Viruses

  1. 1. Bacteria and Viruses Chapter 19
  2. 2. 19.1 Bacteria Come in many shapes and sizes Most common microorganisms are prokaryotes Average size of 1-5 micrometers Compared to eukaryotic cells that are 10- 100 micrometers in diameter
  3. 3. Classifying Prokaryotes Eubacteria Largest prokaryote Domain Cell wall of a carbohydrate- Peptidoglycan Cell membrane around cytoplasm Some have an extra cell wall on the outside to resist damage
  4. 4. Classifying Prokaryotes Archaebacteria Lack nuclei Have cell walls without peptidoglycan Are chemically different from Eubacteria Many live in extremely harsh environments
  5. 5. Identifying Prokaryotes Shapes Bacilli- Rod shaped Cocci- Spherical shaped Sprilla- spiral and cork-screw shaped Colorized SEM 9,000 Colorized SEM 12,000
  6. 6. Identifying Prokaryotes Cell walls Gram staining used to tell them apart Gram+ bacteria look purple Gram- bacteria look pink
  7. 7. Identifying Prokaryotes Movement Flagella Lash, snake or spiral forward They do not move at all
  8. 8. Metabolic Diversity Heterotrophs Chemoheterotrophs: must take in organic molecules for energy and carbon Photoheterotrophs: Use sunlight for energy but need organic compounds for a carbon source
  9. 9. Metabolic Diversity Autotrophs Chemoautotrophs: perform chemosynthesis to make carbon from carbon dioxide. Does not require sunlight Photoautotrophs: use light to convert carbon dioxide and water into carbon compounds and oxygen gas.
  10. 10. Getting Energy  Bacteria need a constant supply of energy Obligate aerobes- require constant supply of oxygen Obligate anaerobes- need no oxygen, for some oxygen will kill it Facultative anaerobes- survive with or with out oxygen
  11. 11. Growth and Reproduction Binary fission Conjugation Spore formation
  12. 12. Importance of Bacteria Decomposers Break down dead matter Nitrogen Fixers Converts nitrogen into a form plants can use Humans use Bacteria
  13. 13. 19.2 Viruses What is a virus? Particles of nucleic acid and proteins Core made up of DNA or RNA surrounded by a capsid Head DNA Need to infect a Tail Tail fiber living host to reproduce
  14. 14. Video on Lytic and Lysogenic Cycle http://www.youtube.com/watch?v=gU8X eqI7yts&feature=related
  15. 15. Viral Infection Lytic Cycle Virus attaches to host cell Injects its DNA Host makes RNA from viral DNA Cell begins to make copies of virus New viruses form Host cell bursts
  16. 16. Viral Infection Lysogenic Cycle Virus attaches to host cell Injects DNA Viral DNA incorporates itself into the host DNA Viral DNA can be dormant Once it becomes active, it follows the 4 processes in the lytic cycle
  17. 17. Phage Phage reproductive cycles Attaches 1 to cell Phage DNA Bacterial chromosome Cell lyses, releasing phages Phage injects DNA 7 2 Many cell 4 divisions Lytic cycle Lysogenic cycle Phages assemble Phage DNA Lysogenic bacterium reproduces Prophage circularizes normally, replicating the prophage at each cell division 3 5 6 OR New phage DNA and Phage DNA inserts into the bacterial proteins are synthesized chromosome by recombination Figure 10.17
  18. 18. Viral Infections Retrovirus: Genetic information is RNA Produces DNA copy and creates a prophage Envelope Glycoprotein Protein coat Example: RNA (two HIV/AIDS identical strands) Reverse transcriptase
  19. 19. 19.3 Diseases Caused by Bacteria and Viruses Pathogens- disease causing agents Bacterial Disease Viral Diseases
  20. 20. Diseases Caused by Bacteria How does bacteria produce disease?  Damage the cells and tissues by breaking down the cells for food Releasing toxins (poisons into the body)
  21. 21. Preventing Diseases Vaccines Immunity Antibiotics
  22. 22. Controlling Bacteria Sterilization Disinfectants Proper food storage
  23. 23. Diseases Caused by Viruses Viruses disrupt the body’s normal equilibrium Cannot be treated with antibiotics Viruses can infect humans and plants
  24. 24. Viruslike Particles Viroids- single stranded RNA molecule with no capsid They cause diseases in plants Infect cell and produce more viroids by disrupting the plant metabolism
  25. 25. Viruslike Particles Prions- contain only protein; no DNA or RNA They cause diseases in animals and humans Prions clump and cause normal protein to clump with it- creating new prions