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Eukaryotes v. Prokaryotes
Prokaryotes Characteristics
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Single cell
No true nucleus
few organelles
Archaebacteria – extreme environments
Eubacteria
Eukaryotes v. Prokaryotes
Eukaryotes
• Larger (up to 100 times!)
• More complex
• Nucleus
• Have chromosomes
• Membrane bound
organelles
• 80S Ribosome
• Animals, plants, protists
Prokaryotes
• Smaller
• Not as complex
• No nucleus
• Have single strand of DNA
and plasmid
• No membrane bound
organelles
• 70S Ribosome
• Bacteria
Chapter 18
Bacteria and Viruses
18.1 Bacteria
Diversity of Prokaryotes
 Bacteria are microscopic organisms that are
prokaryotes.
 Prokaryotes are divided into two domains—
1. Domain Bacteria (eubacteria) and
2. Domain Archaea (archaebacteria).
Chapter 18
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18.1 Bacteria
Archaebacteria
magnification unavailable
Photosynthetic
eubacteria
Eubacteria
9560x
3000x
Chapter 18
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18.1 Bacteria
Eubacteria
 Very strong cell walls
 Determines shape
 Contain peptidoglycan
 Some have a second cell wall
Chapter 18
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18.1 Bacteria
Archaebacteria- aka Extremophiles
 Thermoacidophiles (thur muh uh SIH duh filz)
live in hot, acidic environments.
 Halophiles (HA luh filz) live in very salty
environments.
 Methanogens (meh THAHN oh jenz) cannot live
in the presence of oxygen.
Archaebacteria
• Cell walls made from different materials than
eubacteria
• Cell membrane lipids different from
eubacteria
• DNA sequences are more like eukaryotes than
eubacteria
Chapter 18
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18.1 Bacteria
Differences Between Eubacteria and
Archaebacteria
 The cell walls of the eubacteria contain
peptidoglycan, but the cell walls of
archaebacteria do not.
 The two groups of organisms have different
lipids in their plasma membranes.
 Different ribosomal proteins and RNA
Chapter 18
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18.1 Bacteria
Prokaryote Structure
 Prokaryotes are
microscopic,
unicellular
organisms.
 They have some DNA and ribosomes.
 Lack membrane bound organelles
Chapter 18
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18.1 Bacteria
 Chromosome
(no nucleus)
 May contain extra
DNA in circular
plasmid
Chapter 18
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18.1 Bacteria
 Capsule- protection,
attachment & prevents
dehydration
 Pili- hair-like
projections allowing
for attachment &
reproduction
 Size- very small!
Chapter 18
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18.1 Bacteria
Identifying Prokaryotes
 Shape
 Spherical = Cocci
 Rod-shaped = Bacilli
 Spiral-shaped = Spirochetes
Spirochetes
Bacilli
Cocci
400x
5460x
2000x
Named by Arrangement:
•strep = long chains
•staph = clumps,
•diplo = pairs
•Spirillum/spirochete= corkscrew
•Comma-shaped= vibrio
Chapter 18
Bacteria and Viruses
18.1 Bacteria
Cell Walls
 Eubacterial cells have peptidoglycan.
 Dyes added to the bacteria identify those with
and those without an outer layer of lipid.
Purple = gram positive
cell wall contains peptidoglycan
Chapter 18
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18.1 Bacteria
Movement
 Prokaryotic flagella are made of filaments.
 Flagella help prokaryotes to move toward
materials that they need to survive.
Releasing energy
• Obligate aerobes – carry
out cellular respiration
with oxygen
• Obligate anaerobes –
cannot live in presence of
oxygen
– Clostridium botulinum botulism
• Facultative anaerobes –
can live with or without
oxygen
Chapter 18
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18.1 Bacteria
Reproduction of Prokaryotes
 Binary Fission
 Division of a cell into two
genetically identical cells
 Asexual
 Conjugation
 Two prokaryotes attach to each other and
exchange genetic information.
 Sexual
Chapter 18
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18.1 Bacteria
Survival of Bacteria
 Endospores
 Resistant and able to survive
harsh environments
 Survival advantage!
Chapter 18
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18.1 Bacteria
Mutations
 Bacteria populations grows rapidly.
 Mutations lead to new forms of genes, new
gene combinations, new characteristics, and
genetic diversity.
 Survival advantage!
Chapter 18
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18.1 Bacteria
Modes of Obtaining Nutrients:
Photoautotrophs
 Carry out photosynthesis
Chemoautotrophs
 Break down and release compounds that contain
nitrogen or sulfur
Aerobes and Anaerobes
 Obligate aerobes are bacteria that require oxygen to
grow.
 Anaerobic bacteria do not use oxygen for growth or
metabolism.
Chapter 18
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18.1 Bacteria
Normal Flora
 Most of the bacteria that live in or on you are
harmless and are called normal flora.
21,674x
E. coli
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18.1 Bacteria
Ecology of Bacteria
 Nutrient cycling and nitrogen fixation
 Bacteria are decomposers, returning vital
nutrients to the environment.
 Nitrogen-fixing bacteria live in a symbiotic
relationship in the root nodules of plants
such as soybeans, clover, and alfalfa.
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18.1 Bacteria
Disease-causing Bacteria
 A small percentage of bacteria cause disease.
 Bacteria multiply quickly at the site of infection.
 Bacteria secrete a toxin or break
down tissue.
Bacteria and disease
• Pathogens – disease causing
agents (small percentage of
bacteria)
• Treated with antibiotics – block
the growth and reproduction of
bacteria
Lung infection
Controlling bacteria
• Sterilization – destroy bacteria by subjecting
them to great heat or chemical action
– Disinfectants – chemical solution that kills bacteria
– Refrigeration – bacteria grows more slowly in cold
temps. – food
– Boiling at high temps to kill bacteria
– Salt, vinegar, sugar
Bacteria’s Importance
• Photosynthetic
producers release
oxygen
• Decomposers:
allow recycling of
nutrients
• Oil spill clean up,
sewage treatment
• Nitrogen fixation
produce nitrogen
Chapter 18
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18.1 Bacteria
Foods and Medicines
 Some foods & medicine are made with the aid of
bacteria.
 cheese
 yogurt
 buttermilk
 pickles
 vitamins
 antibiotics
Nitrogen fixers
• Plants depend on nitrogen to
make amino acids and proteins
→animals get nitrogen from plant
proteins
• Nitrogen from atmosphere must
be converted to ammonia NH3
before plants can use it
– This is done by “nitrogen-fixing”
bacteria
– Symbiotic relationship between
plants and bacteria -
Rhizobium
Chapter 18
Bacteria and Viruses
18.2 Viruses and Prions
Viruses
 A nonliving strand of genetic
material within a protein coat
 No organelles to take in
nutrients or use energy
 Cannot make proteins
 Cannot replicate on their own
Structure
• Contain a nucleic acid and
protein
• HEAD region
– Capsid--protein coat with
nucleic acid core
• TAIL region
– to attach to host
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18.2 Viruses and Prions
Viral Infection
 In order to replicate, a virus must enter a host
cell.
 The virus attaches to the host cell using specific
receptor site on the plasma membrane.
 Many viruses cannot be transmitted between
different species.
Figure 19-9 Virus Structures
Section 19-2
Tobacco Mosaic
Virus
T4 Bacteriophage
Head
DNA
Influenza
Virus
RNA
Capsid
proteins
Capsid
RNA
Tail
sheath
Tail
fiber
Surface
proteins
Membrane
envelope
Chapter 18
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18.2 Viruses and Prions
Lytic Cycle
 The host cell makes many copies of the viral
RNA or DNA.
 Lysis of host cell
Lysogenic Cycle
 Viral DNA inserts, or integrates into a
chromosome in a host cell.
 Infected cell will have the viral genes
permanently.
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18.2 Viruses and Prions
Retroviruses
 Viruses that have RNA instead of DNA for
their genetic material
 Contains the enzyme reverse transcriptase
 Retroviruses have a protein capsid.
Chapter 18
Bacteria and Viruses
18.2 Viruses and Prions
Bacteriaphage
 A virus that infects bacteria
Other Viruses
 HIV/AIDS- spread through sexual contact
 Rabies- effects nervous system
 HPV- cancer causing virus
Figure 19-10 Lytic and Lysogenic Infections
Chapter 18
Bacteria and Viruses
18.2 Viruses and Prions
Figure 19-11 Viruses and Cells
Section 19-2
Pathogenic viruses
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Ebola zaire-AIDS
rhinoviruses
influenza
measles, mumps, chicken pox
polio
rabies
smallpox
Vaccines
• “cow pox”--Edward Jenner
– 1796
• Human Papilloma Virus (HPV)- GARDASIL by
Merck
– 2008