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  1. 1. Ch. 19 - Bacteria and Viruses Chapter 19
  2. 2. 19-1 Bacteria • Common name for all prokaryotes • unicellular organisms without a nucleus • Were all in Monera • Eubacteria • live nearly everywhere • normally protected by cell wall containing peptidoglycan - cell membrane inside of cell wall
  3. 3. • Archaebacteria • lack peptidoglycan • DNA similar to eukaryotic DNA • most are extremophiles – live in harsh environments • methanogens; halophiles; extreme thermophiles
  4. 4. Prokaryotic Body Plan pilus DNA bacterial flagellum capsule plasma membrane cell wall ribosomes in cytoplasm cytoplasm
  5. 5. Identifying Prokaryotes 1. Shape a. bacilli(us) – rod-shaped b. cocci(us) – spherical c. spirilla(us) – spiral and corkscrew shaped 2. Cell Walls a. Gram-positive – have thick peptidoglycan cell walls that take and hold stain b. Gram-negative – thinner cell walls with lipids on outside – does not hold stain Gram Positive Gram Negative 3. Movement
  6. 6. Metabolic Diversity 1. Chemoheterotrophs – must take in organic molecules for energy and a supply of carbon 2. Photoheterotrophs – use photosynthesis for energy, but take in organic compounds for carbon source 3. Photoautotrophs – use photosynthesis for both energy and carbon source 4. Chemoautotrophs – use chemosynthesis – get energy from chemical reactions and use carbon dioxide as carbon source
  7. 7. Releasing Energy - bacteria release energy by cellular respiration and fermentation A.Obligate Aerobes - require a constant supply of oxygen B. Obligate Anaerobes - must live in the absence of oxygen C. Facultative Anaerobes - can survive with or without oxygen
  8. 8. Growth and Reproduction - under good conditions bacteria can reproduce every 20 minutes Binary Fission - normal asexual reproduction of bacteria - replicate DNA and then divide Conjugation - exchange of genetic material between bacterial cells - increases genetic diversity Spore Formation - allows survival of bad conditions for a long time
  9. 9. Prokaryotic Fission - 1 bacterial chromosome Bacterium before DNA replication DNA replication begins Figure 21.7 Page 350
  10. 10. Prokaryotic Fission - 2 parent DNA molecule DNA replication completed DNA copy Membrane growth moves DNA molecules apart
  11. 11. Prokaryotic Fission - 3 New membrane and cellwall material deposited Cytoplasm divided in two
  12. 12. nicked plasmid in donor cell Conjugation Transfer of plasmid conjugation tube to recipient cell
  13. 13. Importance of Bacteria - while we usually think of bacteria negatively they are actually essential to correct functioning in ecosystems A. Decomposers - primary decomposers who make nutrients available to plants - used in sewage treatment plants also B. Nitrogen Fixers - Rhizobium in nodules of legume roots fix nitrogen in a form the plants can use
  14. 14. C. Human Uses • in food production • in industry – can clean-up oil spills • to synthesize drugs and chemicals • genetic engineering now has them producing human hormones • Mutualism with Eschecaria coli in our colon where they help us make vitamins