18.4 Bacteria and Archaea
KEY CONCEPT
Bacteria and archaea are both single-celled
prokaryotes.
18.4 Bacteria and Archaea
Prokaryotes are widespread on Earth.
• Prokaryotes can be grouped by their need for oxygen.
– obligate anaerobes
are poisoned by
oxygen
– obligate aerobes
need oxygen
– facultative aerobes
can live with or
without oxygen
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18.4 Bacteria and Archaea
Modes of Nutrition
• Saprobes – feed on dead
organic matter
• Parasites – feed on a host
cell
• Photoautotroph – use
sunlight to make food
• Chemoautotroph – oxidize
inorganic matter such as
iron or sulfur to make food
18.4 Bacteria and Archaea
Bacteria and archaea are structurally similar but have
different molecular characteristics.
• Bacteria commonly come in three forms.
– rod-shaped, called bacilli
– spiral, called spirilla or spirochetes
– spherical, called cocci
Lactobacilli: rod-shaped
Spirochaeta: spiral
• Archaea have many shapes.
Enterococci: spherical
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18.4 Bacteria and Archaea
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18.4 Bacteria and Archaea
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18.4 Bacteria and Archaea
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18.4 Bacteria and Archaea
Clicker Question!
What shape and grouping describes the bacteria
pointed out below?
A: Staphalacoccus
B: Streptobacillus
C: Diplococcus
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18.4 Bacteria and Archaea
Staphylococcus Bacterial
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18.4 Bacteria and Archaea
Streptococcus Causes
Strep Throat
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18.4 Bacteria and Archaea
Bacillus - E. coli
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18.4 Bacteria and Archaea
Streptobacilli
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18.4 Bacteria and Archaea
Spirillum
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18.4 Bacteria and Archaea
Leptospira
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18.4 Bacteria and Archaea
Clicker Question!
1. _________
2. _________
3. _________
4. _________
5. _________
A. Staphylococcus
B. Coccus
C. Spirillum
D. Bacillus
E. Streptococcus
F. Diplococcus
6. _________
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18.4 Bacteria and Archaea
Bacteria
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18.4 Bacteria and Archaea
Archaebacteria
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18.4 Bacteria and Archaea
Methanogens
• Break down
cellulose in a
cow’s
stomach
• Produce
marsh
(methane)
gas
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18.4 Bacteria and Archaea
Extreme Halophiles
• Live in very
salty water
• Use salt to
generate ATP
(energy)
• Dead Sea,
Great Salt
Lake
inhabitants
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18.4 Bacteria and Archaea
Thermoacidophiles or
Thermophiles
• Live in
extremely hot
environments
• Found in
volcanic vents,
hot springs,
cracks on ocean
floor that leak
acid
18.4 Bacteria and Archaea
Clicker Question!
Have a membrane bound
nucleus and organelles:
A: Prokaryotes
B: Eukaryotes
C: Nokaryotes
18.4 Bacteria and Archaea
Bacteria
vs
Archaebacteria
18.4 Bacteria and Archaea
• Bacteria and archaea have similar structures.
– plasmid
– flagellum
pili
plasma
– pili
membrance
chromosome
cell wall
plasmid
This diagram shows the typical structure
of a prokaryote. Archaea and bacteria
look very similar, although they have
important molecular differences.
flagellum
18.4 Bacteria and Archaea
• Bacteria and archaea have molecular differences.
– The amount of peptidoglycan within the cell wall can
differ between bacteria
GRAM NEGATIVE
GRAM POSITIVE
– Archaea have different lipids entirely (cell walls lack
peptidoglycan)
18.4 Bacteria and Archaea
• Gram staining identifies bacteria.
– stains polymer peptidoglycan
– gram-positive stains purple, more peptidoglycan
– gram-negative stains pink, less peptidoglycan
Gram-negative bacteria have a thin layer of
peptidoglycan and stain red.
Gram-positive bacteria have a thicker
peptidoglycan layer and stain purple.
18.4 Bacteria and Archaea
Bacteria have various strategies for survival.
• Prokaryotes
exchange genes
conjugation bridge
during conjugation.
• Bacteria may
survive by forming
endospores.
TEM; magnification 6000x
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18.4 Bacteria and Archaea
Pili in Conjugation
Hairlike structures that help them attach to
surfaces and allow for transfer of genetic
material between two bacteria
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18.4 Bacteria and Archaea
Sticky Bacterial Capsule
Prevents drying out, allows it to attach to
other surfaces, prevents it from being
engulfed, & shelters it from antibiotics
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18.4 Bacteria and Archaea
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18.4 Bacteria and Archaea
Flagella
• Bacteria that are
motile have
appendages
called flagella
• A bacteria can
have one or
many flagella
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18.4 Bacteria and Archaea
Monotrichous
Lophotrichous
Amphitrichous
Peritrichous
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18.4 Bacteria and Archaea
Clicker Question!
What domain can be found
in harsh environments
like: Undersea volcanic
vents, acidic hot springs,
salty water?
A: Bacteria
B: Archaea
C: Eukarea
18.4 Bacteria and Archaea
Clicker Question!
Some bacteria gain energy from
the sun (cyanobacteria), but the
rest have to gain energy by
consuming other organisms.
These are called:
A. Homotrophs
B. Heteroeaters
C. Heterotrophs
D. Homoconsumers
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18.4 Bacteria and Archaea
Clicker Question!
What structure does this
bacterium use for motility?
A: Flagella
B: Cilia
C: Pili
18.4 Bacteria and Archaea
Clicker Question!
Which type of bacteria is susceptible to
antibiotics?
A: Gram Positive (Dark Purple)
B: Gram Negative (Light Pink)
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18.4 Bacteria and Archaea
Clicker Question!
What kind of reproduction is depicted in
the photo below?
A: Asexual
B: Conjugation
C: Binary fission
18.5 Beneficial Roles of Prokaryotes
KEY CONCEPT
Prokaryotes perform important functions for
organisms and ecosystems.
18.5 Beneficial Roles of Prokaryotes
Prokaryotes provide nutrients to humans and other
animals.
• Prokaryotes live in digestive systems of animals.
– make vitamins
– break down food
– fill niches
18.5 Beneficial Roles of Prokaryotes
• Bacteria help ferment many foods.
– yogurt, cheese
– pickles, sauerkraut
– soy sauce, vinegar
18.5 Beneficial Roles of Prokaryotes
Bacteria make Medicine
• Vitamins
• Antibiotics:
–Streptomycin
–Bacitracin
–Tetracycline
–Vancomycin
18.5 Beneficial Roles of Prokaryotes
Prokaryotes play important roles in ecosystems.
• Prokaryotes have many functions in ecosystems.
– photosynthesize
– recycle carbon, nitrogen,
hydrogen, sulfur
– fix nitrogen
18.5 Beneficial Roles of Prokaryotes
• Bioremediation uses prokaryotes to break down
pollutants.
– oil spills
– biodegradable materials
18.6 Bacterial Diseases and Antibiotics
KEY CONCEPT
Understanding bacteria is necessary to prevent
and treat disease.
18.6 Bacterial Diseases and Antibiotics
Some bacteria cause disease.
• Bacteria cause disease by invading tissues or making
toxins.
• A toxin is a poison released by an organism.
18.6 Bacterial Diseases and Antibiotics
• Normally harmless bacteria can become destructive.
– may colonize new tissues
18.6 Bacterial Diseases and Antibiotics
• Normally harmless bacteria can become destructive.
– immune system may be lowered
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18.6 Bacterial Diseases and Antibiotics
Pathogens
STD: Syphilis, gonorrhea, Chlamydia
Respiratory: Strep throat, pneumonia,
whooping cough, tuberculosis, anthrax
Skin: Acne, boils
Digestive: Gastroenteritis, food poisoning,
cholera
Nervous: Botulism, tetanus, bacterial
meningitis
Other: Lyme disease, typhoid fever
18.6 Bacterial Diseases and Antibiotics
Antibiotics are used to fight bacterial disease.
• Antibiotics may stop bacterial cell wall formation.
• Antibiotics do not work on viruses.
• Prevention is best method to fight bacterial disease.
18.6 Bacterial Diseases and Antibiotics
Bacteria can evolve resistance to antibiotics.
• Bacteria are gaining resistance to antibiotics.
A bacterium carries
– overuse
genes for antibiotic
resistance on a plasmid.
– underuse
– misuse
A copy of the plasmid is
through
• Antibiotics must be transferred
conjugation.
used properly.
Resistance is quickly
spread through many
bacteria.