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Chapter 27

Prokaryotes and
the Origins of
Metabolic Diversity
Eukaryote
Classification

Old 5 Kingdom system
• Monera, Protists, Plants, Fungi,
Animals
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Prokaryote
New 3 Domain system
– reflects a greater understanding
of evolution & molecular
evidence
• Prokaryote: Bacteria
• Prokaryote: Archaebacteria
• Eukaryotes
– Protists
– Plants
– Fungi
– Animals
Archaebacteria
&
Bacteria
Prokaryotes
Domain Bacteria
Domain Archaebacteria
Domain
Bacteria
Domain
Archaea
2007-2008
Common ancestor
Domain
Eukarya
Bacteria live EVERYWHERE!

Bacteria live in all ecosystems
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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
Bacterial diversity
Rods(bacilli) and spheres(cocci) and spirals(helical)…Oh My!
eukaryote cell
Prokaryote Structure
prokaryote
cell

Unicellular
– bacilli, cocci, spirilli
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Size
– 1/10 size of eukaryote cell
• 1 micron (1um)
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Internal structure
– no internal compartments
• no membrane-bound organelles
• only ribosomes
– circular chromosome, naked DNA
• not wrapped around proteins
mitochondria
Variations in Cell Interior
cyanobacterium
(photosythetic) bacterium
chloroplast
aerobic bacterium
Prokaryote Cell Wall Structure
Gram-positive bacteria
peptide side
chains
cell wall
peptidoglycan
plasma membrane
protein
That’s
peptidoglycan = polysaccharides + amino acid chains
important for
lipopolysaccharides = lipids + polysaccharides
your doctor
to know!
outer membrane of
Gram-negative bacteria
lipopolysaccharides
cell wall
outer
membrane
peptidoglycan
plasma
membrane
Motility
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1- Flagella
2- Helical shape
(spirochetes)
3- Slime
4-Taxis
(movement away or
toward a
stimulus)
QuickTime™ and a
Cinepak decompressor
are needed to see this picture.
Form & Function
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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!)
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
conjugation
– direct transfer of DNA
Nutrition & Metabolism
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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
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
•Koch’s 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)
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