Prokaryotes And The Origins of Metabolic Diversity

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Prokaryotes And The Origins of Metabolic Diversity

• Kingdom Monera

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The Oldest Organisms

• Oldest fossils go back 3.5 bya
• Chemical cycles evolved in prokaryotes
• Wide range of modes of nutrition
• Est. diversity of up to 4 million species
• Two main brances are archaea and bacteria

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The Three Domains
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Comparing Domains
CHARACTERISTICS BACTERIA ARCHAEA EUKARYA
Peptidoglycan in cell wall Present Absent Absent
RNA Polymerase One kind only Several kinds Several kinds
Initiator amino acid in protein synthesis Formyl-methionine Methionine Methionine
Histones associated with DNA None Present Present
Introns in genes None Some Present
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Three Common Shapes
Spheres - Cocci
Rods - Bacilli
Helices Spirilla, spirochetes
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Classification By Gram Stain
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Gram Positive and Gram Negative Bacteria
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Pilli

• Allow bacteria to attach to a substrate
• Allow for exchange of plasmids during conjugation
• Not present in all bacterial groups

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Some Bacteria Are Motile

• Bacilli may move using one or more flagella
• Narrower than eukaryotic flagella
• Lack membrane covering
• Not a 92 pattern
• Exhibit taxis chemo or photo

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Flagella
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Reproduction and Genetic Recombination

• Asexual reproduction by binary fission 20min.
  in log phase growth
• Three mechanisms of genetic recombination
• 1. transformation
• 2. conjugation
• 3. transduction
• Mutation is the major source of genetic variation

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Bacilli Produce Endospores

• Bacillus anthracis
• Resistant capsule
• Survives many attempts destroy it
• Requires sterilization with heat and pressure
• Steam at 15 lbs. per sq. in. for at least 20 min.

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Nutrition and Metabolic Diversity
Mode of Nutrition Energy Source Carbon Source Type of Organism
Photoautotrophs Sunlight CO2 Cyanobacteria, certain protists (algae)
Chemoautotrophs Inorganic Chemicals (H2S, NH3, Fe2) CO2 Sulfur bacteria
Photoheterotrophs Sunlight Organic molecules Certain prokaryotes
Chemoheterotrophs Organic molecules Organic molecules Animals, fungi, many protists, prokaryotes, parasitic plants
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Evolution of Photosynthesis
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Archaea

• Methanogens use CO2 to oxidize H2 into CH4
• Exteme halophiles (Bacteriorhodopsin is their
  photosynthetic pigment. Purple color)
• Extreme thermophiles Oxidize sulfur for energy
  at deep-sea thermal vents at 105ºC

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Ecological Impact of Prokaryotes

• Decomposers Recycle chemical elements between
  biological and physical components of the
  ecosystem
• Fix carbon (as CO2) and nitrogen (as NH3)
• Produce O2 (cyanobacteria)
• Symbiotic
• mutualism cyanobacteria in root nodules
• commensalism bacteria in/on the body
• parasitism pathogenic bacteria
• Streptomyces Source of our antibiotics

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Kochs Postulates

• Find the same pathogen in each diseased
  individual.
• Isolate pathogen from diseased individual and
  grow it in pure culture.
• Induce disease using pure culture.
• Re-isolate pathogen from individuals in which
  disease was induced from pure culture.
• Doesnt work for all pathogens (Treponema
  pallidum, the cause of syphilis, cant be
  cultured on media)

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Exotoxins

• Proteins secreted by prokaryotes
• Clostridium botulinum botulism (botox)
• Vibrio cholerae Cholera (severe diarrhea)
• E. coli Travellers diarrhea

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Endotoxins

• Components of the outer membranes of certain
  gram-negative bacteria
• Genus Salmonella Causes food poisoning
• Actinomycetes Fungus-like prokaryotes
• 1. Mycobacterium sp. (Tuberculosis leprosy)
• 2. Streptomyces sp. (Antibiotics)

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Benefit to Society

• Remove pollutants from soil, water, or air
• Oil spills
• Sewage treatment
• Production of drugs by genetic engineering
• Prevention of freeze damage to crops
• Antibiotic production