Prokaryotes and the Origins of Metabolic Diversity

1
Chapter 27

• Prokaryotes and the Origins of Metabolic
  Diversity

2
Classification

• Old 5 Kingdom system
• Monera, Protists, Plants, Fungi, Animals
• New 3 Domain system
• reflects a greater understanding of evolution
  molecular evidence
• Prokaryote Bacteria
• Prokaryote Archaebacteria
• Eukaryotes
• Protists
• Plants
• Fungi
• Animals

3
Prokaryotes

• Domain Bacteria
• Domain Archaebacteria

4
Bacteria live EVERYWHERE!

• Bacteria live in all ecosystems
• on plants animals
• in plants animals
• in the soil
• in depths of the oceans
• in extreme cold
• in extreme hot
• in extreme salt
• on the living
• on the dead

5
Bacterial diversity
Rods(bacilli) and spheres(cocci) and
spirals(helical)Oh My!
6
Prokaryote Structure

• Unicellular
• bacilli, cocci, spirilli
• Size
• 1/10 size of eukaryote cell
• 1 micron (1um)
• Internal structure
• no internal compartments
• no membrane-bound organelles
• only ribosomes
• circular chromosome, naked DNA
• not wrapped around proteins

7
Variations in Cell Interior
cyanobacterium(photosythetic) bacterium
aerobic bacterium
internal membranesfor respirationlike a
mitochondrion(cristae)
internal membranesfor photosynthesislike a
chloroplast(thylakoids)
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Prokaryote Cell Wall Structure
Thatsimportant foryour doctorto know!
peptidoglycan polysaccharides amino acid
chains lipopolysaccharides lipids
polysaccharides
9
Motility

• 1- Flagella
• 2- Helical shape (spirochetes)
• 3- Slime
• 4-Taxis (movement away or toward a stimulus)

10
Form Function

• Nucleoid region (genophore non-eukaryotic
  chromosome)
• Plasmids
• Asexual reproduction binary fission (not
  mitosis)
• Sexual reproduction (not meiosis)
  transformation uptake of genes from surrounding
  environment conjugation direct gene
  transfer from 1 prokaryote to another
  transduction gene transfer by viruses
• Endospore resistant cells for harsh conditions
  (250 million years!)

11
Genetic variation in bacteria

• Mutations
• bacteria can reproduce every 20 minutes
• binary fission
• error rate in copying DNA
• 1 in every 200 bacteria has a mutation
• you have billions of E. coli in your gut!
• lots of mutation potential!
• Genetic recombination
• bacteria swap genes
• plasmids
• small supplemental circles of DNA
• conjugation
• direct transfer of DNA

conjugation
12
Nutrition Metabolism

• Photoautotrophs photosynthetic harness light to
  drive the synthesis of organics (cyanobacteria)
• Chemoautotrophs oxidation of inorganics for
  energy get carbon from CO2
• Photoheterotrophs use light to generate ATP but
  get carbon in an organic form
• Chemoheterotrophs consume organic molecules for
  both energy and carbon saprobes- dead organic
  matter decomposers parasites- absorb
  nutrients from living hosts
• Oxygen relationships obligate aerobes
  facultative anaerobes obligate anaerobes

13
Bacteria as pathogens

• animal diseases
• tooth decay, ulcers
• anthrax, botulism
• plague, leprosy, flesh-eating disease
• STDs gonorrhea, chlamydia
• typhoid, cholera
• TB, pneumonia
• lyme disease

opportunistic normal residents of host cause
illness when defenses are weakened
Kochs postulates criteria for bacterial
disease confirmation exotoxins bacterial
proteins that can produce disease w/o the
prokaryote present (botulism)
endotoxins components of gram - membranes
(Salmonella)
14
Bacteria as beneficial ( necessary)

• Life on Earth is dependent on bacteria
• decomposers
• recycling of nutrients from dead to living
• nitrogen fixation
• only organisms that can fix N from atmosphere
• needed for synthesis of proteins nucleic acids
• plant root nodules
• help in digestion (E. coli)
• digest cellulose for herbivores
• cellulase enzyme
• produce vitamins K B12 for humans
• produce foods medicines
• from yogurt to insulin