Prokaryotes

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Prokaryotes
The Origins of Metabolic Diversity
Lightning Strike
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The World of Prokaryotes

• Prokaryotes were the earliest organisms
• They are not only the most numerous organisms,
  but also the most pervasive
• Prokaryotes are microscopic and perform vital
  functions
• Prokaryotes often live in symbiotic relationships
  endosymbiosis

p. 502 - 503
Tornado on the road
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p. 503
Point of reference
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An Explosion of Diversity

• Modern prokaryotes are diverse in structure and
  physiology
• About 5000 species are known
• Estimated range 400,000 4 million
• A true sense of biodiversity requires a
  downward adjustment of scale

p. 503
Hydrogen Explosion
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Bacteria and Archaea

• The two main branches of prokaryotic evolution
• Archaeabacteria are much closer to eukaryotes
  than they are to eubacteria
• Archaea inhabit extreme environments (hot
  springs, salt ponds, thermal vents)

A thermal vent ?
p. 503
Cool Harvard Cell Video
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Prokaryotic Structure

• Most prokaryotes are unicellular
• Some species tend to form aggregates
• Others form true colonies while few exhibit
  multicellular characteristics
• Nearly all prokaryotes have cell walls external
  to their plasma membranes
• Bacterial walls consist of peptidoglycan (polymer
  of modified sugars cross-linked with short
  polypeptides) archaea lack peptidoglycan

p. 504
Cool Harvard Cell Video
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Average prokaryote diameter 1 5 µm Average
eukaryotic diameter 10 100 µm The largest
prokaryote Bacilli measuring ½ mm
p. 504
Among pathogens, gram-negative are more
threatening because they are more resistant to
antibiotics (i.e. penicillin) that degrade
peptidoglycan Capsule sticky protective
secretion on prokaryotes that provides protection
Gram stains Gram-positive simpler walls and
abundant peptidoglycan Gram-negative complex
with low peptidoglycan outer membrane contains
lipopolysaccharides (carbohydrate bonded to lipid)
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Motility

• About half of prokaryotes are motile
• Many move through solutions of water, ions, and
  other solutes
• Many motile prokaryotes can move about 50 µm/sec
• Flagellar movement
• Spirochete movement
• Most are capable of taxis (movement toward/away
  from a stimulus
• Magnetic particles establish up and down
• Photosynthetic bacteria show positive phototaxis

Spirochete
p. 506
Eubacteria Archaeabacteria
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Cellular and Genomic Organization

• Prokaryotes lack the extensive eukaryotic
  compartmentalization
• Bacteria have smaller, simpler genomes
• Genophore prokaryotic chromosome
• DNA is concentrated in a snarl of fibers in a
  nucleoid region
• Plasmids may also be present
• The prokaryotic ribosome is smaller

p. 506
Black Hole in Space
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Reproduction and Variation

• Binary fission continuous DNA synthesis and
  indefinite asexual multiplication
• Three methods of genetic recombination
• Transformation genetic material taken from the
  environment
• Conjugation genes transferred directly between
  prokaryotes via sex pilius
• Transduction genes transferred between
  prokaryotes and viruses
• Mutation remains the largest source of variation
• Populations of prokaryotes grow and adapt rapidly
• Growth in prokaryotes refers to population size
  more than individual cell enlargement
• Some bacteria form resilient cells called
  endospores around their DNA, encasing it against
  most degrading elements

Variations in endospore morphology (1, 4)
Central endospore (2, 3, 5)
Terminal endospore (6) Lateral
endospore
p. 507
Binary Fission
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Nutritional and Metabolic Diversity

• Photoautotroph Organisms that harness light
  energy to drive photosynthesis with CO2
  (cyanobacteria)
• Chemoautotroph Organisms that need only CO2 to
  oxidize inorganic substances with chemical energy
  from hydrogen sulfide (H2S), ammonia (NH3), and
  ferrous ions (Fe2) or other molecules
• Photoheterotroph Organisms that use light to
  generate ATP, but obtain carbon in organic form
• Chemoheterotroph Organisms that consume organic
  molecules for both energy and carbon

p. 508
The Toba Eruption
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p. 508 509
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Nutritional Diversity Among Chemoheterotrophs

• Saprobes Decomposers that absorb their nutrients
  from dead organic matter
• Parasites Organisms that absorb their nutrients
  from body fluids of living hosts
• Nitrogen Metabolism
• Nitrogen fixation p. 1141

p. 508 509
Supernova Explosion
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Metabolic Relationships to Oxygen

• Obligate aerobes use O2 for cellular respiration
  and cannot grow without it
• Obligate anaerobes are poisoned by O2 which live
  either exclusively on fermentation or extract
  chemical energy through anaerobic respiration
• Facultative anaerobes will use O2 is it is
  present but can also undergo fermentation

p. 509
Quasar
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The Bacteria Song!!!

• Before we move to some facts

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Fun Facts

• Prokaryotes have a higher metabolic rate than
  eukaryotes due to their large surface area to
  volume ratio
• Cyanobacteria often live in differentiated
  colonies, showing small signs of specialization
• We are made of dead star meterial
• Black holes are gravitys revenge on mass

Neptunes Great Dark Spot
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Thank you! Thank you very much!