Ch. 27 Bacteria and Archaea
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Transcript of Ch. 27 Bacteria and Archaea
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Ch. 27 Bacteria and
ArchaeaObjective:
Understand the general structure and motility of bacteria and how genetic recombination increases
diversity.
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27.1 Structural and Functional Adaptations Contribute to Prokaryotic
Success• Very adaptable (extreme salt, pH, and temp).• Most are unicellular (0.5-5 um) but still perform
all of life’s functions.
(a) Spherical (b) Rod-shaped (c) Spiral
1 m
1 m
3 m
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Cell Surface Structures
• All bacteria have a cell wall.• Archaeal bacteria do NOT have a layer of peptidoglycan
in their cell walls.• Eubacteria have differing amount of peptidoglycan
o Gram positive: stains violet due to thick layer peptidoglycan.o Gram negative: stains red due to extra membrane past
peptidoglycan.(a) Gram-positive bacteria: peptidoglycan traps crystal violet.
Gram-positivebacteria
Peptido-glycanlayer
Cellwall
Plasmamembrane
10 m
Gram-negativebacteria
Outermembrane
Peptido-glycanlayer
Plasma membrane
Cellwall
Carbohydrate portionof lipopolysaccharide
(b) Gram-negative bacteria: crystal violet is easily rinsed away, revealing red dye.
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Motility• About half of known bacteria can move (taxis)
toward/away from a stimuluso Most commonly via flagella either surrounding the body or found at 1
end. Works like a helicopter with a motor, hook, and filament.
Flagellum
HookMotor
Filament
RodPeptidoglycanlayer
Plasmamembrane
Cell wall
20 nm
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Internal Organization and DNA
• No membrane bound organelles but plasma membrane folds on itself to make metabolic membranes.
(a) Aerobic prokaryote (b) Photosynthetic prokaryote
Respiratorymembrane
Thylakoidmembranes
0.2 m 1 m
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Internal Organization and DNA
• Smaller, circular DNA found in nucleoid (not nucleus) with very small plasmids (self replicating DNA)
Chromosome Plasmids
1 m
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Reproduction and Adaptation
• Reproduce every couple of hours (under optimal conditions) by binary fission.o Division stops due to space limits, metabolic toxins, eaten, etc.o Short generation time leads to quick evolution.
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Reproduction and Adaptation
• Endospores develop in harsh conditions.o Duplicated DNA in a tough, multilayered structure.o Water is removed and metabolism stops.
Coat
Endospore
0.3 m
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27.2 Rapid Reproduction, Mutation, and Genetic Recombination Promote Genetic Diversity in
Prokaryotes
• 3 mechanisms for prokaryotic genome combinationso Transformationo Transductiono Conjugation
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Transformation• Changes genotype
and phenotype by uptake of foreign DNAo Ex: harmless strains of the
bacteria that can cause pneumonia become pathogenic if they come in contact with a pathogenic cell.
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Transduction• A “mutant” phage
with bacterial DNA infects a bacteria cell.
Recombinant cell
Recipientcell
Recombination
A
A
A B
BA
Donor cell
A B
BA
Phage
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Conjugation• A donor bacteria makes a copy of its DNA,
attaches to another bacteria via a (sex) pilus, the DNA travels to recipient forming a recombined cell.
Sex pilus
1 m
F plasmid Bacterial chromosome
F cell(donor)
F cell(recipient)
Matingbridge
Bacterialchromosome
(a) Conjugation and transfer of an F plasmid
Hfr cell(donor)
F cell(recipient)
(b) Conjugation and transfer of part of an Hfr bacterial chromosome
F factor
A
A
A
A
A
A A
F cell
F cell
AA
RecombinantF bacterium
A