Bacteria
18.4
Bacteria and Archaea
KEY CONCEPT
Bacteria and archaea are both single-celled
prokaryotes.
TEKS 8C
What are Bacteria?
• Prokaryotes - Cells that do not have their
DNA contained in a nucleus (All Bacteria!)
• There are two Kingdoms of unicellular
prokaryotic organisms:
– Archaebacteria
– Eubacteria (“eu” meaning true bacteria).
Archaebacteria
• In their own domain Archaea because they
are so different molecularly from true
bacteria.
– They are prokaryotic, unicellular and live in
extreme environments (no oxygen, high salt,
high temperatures, etc.)
– Their cells walls do not contain peptidoglycan.
Eubacteria
• In the Domain Bacteria.
– They are prokaryotic, unicellular, and live all
over the world, around, in and on organisms
(yes, all inside of you!)
– Their cell walls are made of peptidoglycan.
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.
TEKS 8C
flagellum
Parts of Bacteria
1. Plasma (cell) membrane- selectively
permeable for material exchange
2. Cell Wall- made of peptidoglycan in Eubacteria
3. DNA- contained in a “nucleoid region”
4. Pili- small protein extensions used to anchor
themselves OR sex pili aid in exchanging DNA
5. Flagella- whip-like tail for movement
6. Ribosomes- translate genetic material into
proteins
18.4
Bacteria and Archaea
TEKS 8C
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
18.4
Bacteria and Archaea
TEKS 8C
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
Coccus
Spirillum
Bacillus
18.4
Bacteria and Archaea
TEKS 8C
• 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
Classification- Gram staining
• Bacteria are identified by how THICK their
cell wall is. Scientists use a method called
Gram staining to identify certain kinds of
bacteria.
– Gram + : bacteria stains purple, meaning they
have a thick cell wall of peptidoglycan
– Gram - : bacteria stains light pink (or red),
meaning they have a thin wall of 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.
TEKS 8C
Metabolism
• Bacteria can be classified by how they
obtain energy and use it. They can be…
– heterotrophs (must consume food)
– autotrophs (can make their own food).
• Chemoautotroph – make their own food starting
with inorganic molecules
• Photoautotroph – make their own food using light
Reproduction
• Most bacteria reproduce very quickly by a
process called binary fission, some only taking
20 minutes to divide.
• They reproduce asexually, meaning they simply
divide without combining genetic material.
• Small parts of DNA can be exchanged through
sex pili. They act like little tunnels through which
DNA can be exchanged.
18.4
Bacteria and Archaea
TEKS 8C
Bacteria have various strategies for survival.
• Prokaryotes
exchange genes
conjugation bridge
during conjugation.
• Bacteria may
survive by forming
endospores.
TEM; magnification 6000x
18.5
Beneficial Roles of Prokaryotes
KEY CONCEPT
Prokaryotes perform important functions for
organisms and ecosystems.
TEKS 11C
Importance of Bacteria
• We think of bacteria as being all bad, but
actually we need them greatly!
• Bacteria are vital to maintaining the living
world.
Human uses
• We have bacteria living on all surfaces of
our bodies and ones such as E. coli are
essential for our digestion. We provide
them with a warm environment, and they
provide us with essential vitamins that we
cannot produce on our own. This too is a
mutualistic symbiotic relationship.
18.5
Beneficial Roles of Prokaryotes
• Bacteria help ferment many foods.
– yogurt, cheese
– pickles, sauerkraut
– soy sauce, vinegar
TEKS 11C
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
TEKS 11C
Importance
2. Decomposers: when all organisms die,
their organic matter must be returned to
the soil for other organisms.
Decomposers complete the carbon cycle.
Pathogens- harmful bacteria
• Any disease causing agent is called a
pathogen- it could be bacterial or viral
• Harmful Bacteria-cause disease in one of
two ways:
– Breaking down our body’s cells as food
– Releasing toxins that travel through the body
and damage our cells
18.6
Bacterial Diseases and Antibiotics
TEKS 7F, 11C
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
TEKS 7F, 11C
• Normally harmless bacteria can become destructive.
– may colonize new tissues
18.6
Bacterial Diseases and Antibiotics
TEKS 7F, 11C
• Normally harmless bacteria can become destructive.
– immune system may be lowered
Lyme Disease

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Cause: Borrelia
burgdorferi
Symptoms: fever,
fatigue, headaches,
muscle aches, joint
aches, Bulls-eye
shaped rash
Transmission: tick bite
Treatment: antibiotics
Tetanus (Lock jaw)

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Cause: Clostridium tetani
Toxins released by bacteria
interfere with nervous system
Symptoms: Severe muscle
spasms and possibly death
Transmission: Commonly
contracted from deep puncture
wound or self-piercing with
contaminated materials
Tetanus (Lock jaw)

Treatment:
–
–
–
Clean wound
Mild: given antibodies
against it, with antibiotics,
and a vaccine
Severe: same as above,
muscle relaxers or even
paralytic drugs to stop the
spasming
Tuberculosis (TB)
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Affects nearly 1/3 of the
world’s population
Cause: Mycobacterium
tuberculosis
Symptoms: Fatigue, weight
loss, fever, chronic cough
Tubercles form in lungs
(dormant form)
Transmission: Spread
through cough
Treatment: long term
antibiotic treatment (6-12
months)
Gonorrhea
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Cause: Neisseria
gonorrhoeae
Male symptoms:
–
–
–

Thick, foul-smelling
discharge from penis
Painful urination
Testiculur and abdominal
pain
Female symptoms:
–
–
–
Pus-like vaginal discharge
Pain urinating
Bleeding after intercourse

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Transmission: oral, anal, or
vaginal sex
Treatment: with antibiotics
Chlamydia

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
One of the most common STIs on
college campuses
Cause: Chlamydia trachomatis
Symptoms: Burning during
urination, discharge from the penis
or vagina, pain and itching


Transmission: oral, anal, or
vaginal sex; mother to child
during childbirth through
vaginal canal
Treatment: with antibiotics
Strep Throat

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Cause: Streptococcus
pyogenes, certain strains
cause scarlet fever and Toxic
Shock Syndrome
Symptoms: fever, sore throat,
swollen glands
Transmission: respiratory
droplets (coughing sneezing)
Treatment: antibiotics can
cause it to go away faster
Purple  gram +
Tooth Decay

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Cause: Streptococcus
mutans, bacteria doubles in
24 hours
Symptoms: Destruction of
tooth enamel
Transmission: resident in
mouth
Treatment: brush and floss
daily
Bacterial meningitis

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Cause: Neisseria
meningitis
Symptoms: high fever,
headache, stiff neck,
nausea, fatigue
Transmission: most
common in college dorms
Treatment: antibiotics,
early detection is
essential
Anthrax

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Used in Bioterrorism
Cause: Bacillus anthracis, a spore-forming bacteria
Transmission/Symptoms of varying types:
– Spread by eating undercooked meat (vomiting and diarrhea,
possible death)
– breathing in spores (usually fatal)
– skin contact (ulcers, rashes, not fatal)
Treatment: oral and IV antibiotics
Botulism- food poisoning

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Cause: Clostridium botulinum
Symptoms: blurred vision, slurred
speech, difficulty swallowing,
muscle weakness, paralysis
Transmission: From a wound,
contaminated food
Treatment: antibiotics
FACTOID: Botox is a toxin
secreted by Clostridium botulinum
Staphylococcus aureus
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Pets can carry bacteria as well!
Staphylococcus aureus
–
–
–
–
Gram +
Cause: Staphylococcus aureus
Symptoms: nausea, cramping,
retching; some individuals may not
show symptoms
Transmission: eating contaminated
food, contaminated air, individuals and
surfaces

PETS!
Preventing Disease
1. Good hygiene- wash hands thoroughly
with soap and water (you don’t need
antibacterial!!!), brush teeth and floss
(bacteria in your mouth DOUBLES in 24
hours); take care with who your drink after,
check ups at the doctor
Preventing Disease
2. Vaccine- a weakened or dead form of the
pathogen is given to a patient whose body
will form an immune response to it. Once
that immune response happens, your body
remembers it forever and if the real
pathogen gets in your body, your immune
system will react quickly and kill it
immediately.
Preventing Disease
3. Antibiotics- if infection
does occur, antibiotics
can be given. They
prevent growth and
division of bacteria so
that our immune
systems can conquer the
illness more easily.
Unfortunately, bacteria
evolve in response to
this pressure and we
have many antibiotic
resistant diseases now.