The Diversity of Viruses, Prokaryotes and Protists 2: Focus on Prokaryotes

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The Diversity of Viruses, Prokaryotes and
Protists 2 Focus on Prokaryotes
Chapter 19
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Prokaryotic Domains

• The Prokaryotes include
• Domain Bacteria
• Domain Archaea
• Bacteria and Archaea are distinct from each other
  microscopically (i.e. cell wall structure) and
  biochemically.
• Difficult to classify wont get into here

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Prokaryotic Domains

• Three common prokaryote shapes

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Prokaryotes

• Some prokaryotes use flagella for propulsion
• Wheel and axle type structure embedded in
  plasma membrane and cell wall

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Prokaryotes

• Bacteria often form biofilms
• Aggregation of slime-secreting colonies
• Often difficult to remove or kill
• Example Dental plaque

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Prokaryotes

• Protective endospores allow some bacteria to
  withstand adverse conditions
• Rod-shaped bacteria form endospores
• Form inside the cells
• Contain genetic material enzymes encased in a
  protective coat
• Resistant to extreme conditions
• Can survive for extraordinarily long periods
• In one case, 250 million year old endospores were
  found to be viable!
• The bacteria that causes anthrax forms
  endospores, making them (unfortunately) ideal for
  biological weapons.

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Prokaryotes

• Most reproduce by fission (simple form of cell
  division asexual)
• High reproduction rates (1 division/20 min)
• 1 cell ? 1021 cells in a day!
• Leads to high mutation rates
• Unfixed errors during replication ? mutation

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Prokaryotes

• Some Bacteria and Archaea can exchange genetic
  material via conjugation.
• Cells temporarily fuse and form cytoplastmic
  bridge for movement of DNA between cells
• Some bacteria extend sex pili to attach to
  recipient cells
• Small, circular DNA called plasmids are
  transferred (separate from the main DNA of the
  cell)

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Prokaryotes

• Prokaryotes are specialized for specific habitats
• Around boiling point (Yellowstone Hotsprings),
  and even above boiling point (deep sea vents at
  110ºC)
• 1.7 miles below Earths surface!
• Frozen in ice!
• Dead Sea (7 times saltier than the ocean!)
• Dormant in an 11,000 year old dead Mammoth!
• Human bacteria specialize on certain body regions.

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Prokaryotes

• Diverse metabolism
• Some are anaerobic some are aerobic, some switch
  between the two
• O2 is toxic to some anaerobes
• Some can derive energy from organic compounds
  such as petroleum or benzene
• How could these be useful to humans?
• Some can metabolize inorganic molecules
  (hydrogen, sulfur, iron, ammonia, nitrite)
• Example Your fish tank!

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Prokaryotes

• Diverse metabolism (cont.)
• Cyanobacteria are photosynthetic
• No chloroplasts have special chlorophyll-containi
  ng membranes
• Some deep-sea bacteria are chemosynthetic
  autotrophs, using sulfur rather than sunlight for
  energy (and H2S rather than H20 for source of
  hydrogen ions)

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Prokaryotes

• Mutualistic relationships
• Help plant-eating animals break down plant
  material
• Cows, rabbits, deer, etc
• Assist in vitamin synthesis (i.e. vitamin K, B12)
• Fix atmospheric nitrogen needed by plants
• In soil and water
• Associated with the roots of legumes (alfalfa,
  peas and beans, clover, lupines, etc)

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Prokaryotes

• Impact on human health
• Botulism and tetanus attack the nervous system
• Thrive in oxygen-free environments (i.e. a
  sealed, improperly sterilized can of food)
• Numerous diseases
• Plague
• Lyme disease
• Tuberculosis
• Cholera
• Common bacteria gone bad
• Streptococcus (some strains)
• Flesh eating infection
• E. coli (some strains)

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Prokaryotes

• Impact on human health
• Most bacteria are harmless!
• And many are helpful (see mutualistic
  relationships)