Transcript unit 4 bacteria

Microbiology –
Bacterial Structures
-Not all bacteria have all structures
Shapes of Bacteria
• 3 Different Shapes:
Bacilli
• Rod shaped
• Most occur singly, but some form long
chains called Streptobacilli
• Examples:
– Typhoid fever
– Anthrax
– Diptheria
Typhoid Fever
• Typhoid fever — a common worldwide bacterial
disease transmitted by the ingestion of food or water
contaminated with the feces of an infected person
• Caused by the bacterium Salmonella enterica
• The incubation period is usually 1-2 weeks, and the
duration of the illness is about 3-4 weeks. Symptoms
include:
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Poor appetite
Headaches
Generalized aches and pains
Fever as high as 104
Lethargy
Diarrhea
Anthrax
• Anthrax is an acute disease caused by the bacterium
Bacillus anthracis.
• Most forms of the disease are lethal, and it affects
both humans and animals.
• There are effective vaccines against anthrax, and
some forms of the disease respond well to antibiotic
treatment.
• Can form dormant endospores that are able to
survive in harsh conditions for decades or even
centuries.
• When spores are inhaled, ingested, or come into
contact with a skin lesion on a host, they may
become reactivated and multiply rapidly.
Anthrax Letters 2001
http://www.fbi.gov/aboutus/history/famous-cases/anthraxamerithrax
• Right after 9/11/01 letters
containing Anthrax spores
post marked Trenton. NJ
were sent to NYC and
Washington DC.
• Five Americans were killed
and 17 were sickened with
Anthrax.
• The FBI, Justice Department,
US Postal Service, and other
law enforcement agencies
conducted a 10 year
investigation
which concluded Dr. Bruce Ivins,
a US bio-weapons specialist was
responsible.
Cocci
• Usually sphere shaped but can be oval
• Diplococci – cocci that remain in pairs
– Examples – Gonorrhea, Menengitis
• Streptococci – cocci in chains
– Examples - Strep throat, Tooth decay
• Staphylococcus – irregular grape-like
cluster of cells
– Examples – Food poisoning, staph skin
infections
Staph Infections
• Methicillin-resistant Staphylococcus aureus (MRSA) infection is
caused by a strain of staph bacteria that's become resistant to the
antibiotics commonly used to treat ordinary staph infections.
• Two types: healthcare HA-MRSA and community CA-MRSA.
• (CA-MRSA), often begins as a painful skin boil. It's spread by
skin-to-skin contact. At-risk populations include groups such as
high school wrestlers, child care workers and people who live in
crowded conditions.
Meningitis
• Meningitis is an infection of the membranes
(meninges) surrounding the brain and spinal cord.
• The bacteria most often responsible for bacterial
meningitis are common in the environment and can
also be found in your nose and respiratory system
where it is harmless.
• Sometimes meningitis occurs for no known reason.
Other times it occurs after a head injury or after you
have had an infection and your immune system is
weakened. Often occurs at college campuses.
• The onset of symptoms is fast, within 24 hours. If
allowed to progress, you can die from bacterial
meningitis.
Spiral Bacteria
• Vibrios – curved rods - look like a
comma
– Example - Cholera
• Spirilla – corkscrew shape with flagella
– Example – Rat Bite fever
• Spirochetes – corkscrew shape but no
flagella
– Example - syphilis
Cholera
• Cholera is an infection of the small intestine caused
by the bacterium Vibrio cholerae.
• The main symptoms are watery diarrhea and
vomiting.
• Transmission occurs primarily by drinking water or
eating food that has been contaminated by the feces
of an infected person, including one with no
apparent symptoms.
Syphilis
• Syphilis is a sexually transmitted infection caused by
the spirochete bacterium Treponema pallidum
• The primary route of transmission is through sexual
contact.
• Primary syphilis - develop one or more sores on the
genitals or in or around the mouth
• Secondary stage - rosy rash typically on the palms of
the hands and soles of the feet. Also moist warts in
the groin, white patches on the inside of the mouth,
swollen lymph glands, fever, and weight loss.
• Tertiary syphilis - severe problems with the heart,
brain, and nerves that result in paralysis, blindness,
dementia, deafness, impotence, and death.
Flagella
• Used by some bacteria to achieve
motion
• Made of long rigid strands of protein
called flagellin
• Protein strands are permanently coiled
• Permits the flagellum to rotate and
propel the bacterium forward
Flagella
•
3-D coiled protein filament attached to
hook-like shaft passes through cell wall
and attached to bacteria cell membrane.
Flagella
Monotrichous
Lophotrichous
Amphitrichous
Peritrichous
Axial Filament
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Spirochetes ONLY
One flagella attached at both ends of
flexible spiral microorganism
Motion effected by cell spinning around
filament
Pili
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Look like short flagella but have nothing
to do with motion
Very tiny protein “hairs” that enable
bacteria to stick to surfaces - like
“Velcro”
Pili
• Pili aid in transfer of genetic material
between bacteria
• Pili anchor bacteria to surfaces like
living tissue
• Can enhance bacterial disease effect
• Example - gonorrhea
Capsule
• Some bacteria secrete a layer of
polysaccharides and proteins that stick
to its surface
• Sticky and gelatinous
• Serves as a buffer between the bacteria
and its environment
– Protects bacteria against dehydration
– Protects bacteria against host’s immune
system
Glycocalyx
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Some bacteria produce a Slime Layer
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Complex sugar, made inside cell wall secreted
as liquid, polymerizes to jelly like substance
Cavities – S. mutans attaches itself to teeth by
using the sugar a person eats – creates an
acid that breaks down tooth enamel
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Cell Wall
• All bacteria EXCEPT MYCOPLAMAS have
a cell wall
• Semi-rigid structure, protects, gives
shape
• Amount of chemical “Peptidoglycan”
determines characteristics of cell wall
• If a lot: Thick, G+ stain reaction, sensitive
to penicillin and lysozyme in tears, saliva,
mucous
•Small, thin wall: G-stain positive, not
sensitive to penicillin or lysozyme
•If bacteria is pathogenic, disease more
difficult to cure
Cell Membrane
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Boundary layer of the cell inside of cell wall
Contains Cytoplasm, controls molecular traffic
in and out of the cell
Triple layer structure, 60% proteins, 38% lipids
(phospholipid bilayer), 2% sugars
Antimicrobials (detergents, alcohol, some
antibiotics) dissolve cell membrane
Cytoplasm
Gelatinous mass of
proteins
carbohydrates
lipids
nucleic acids
salts
ions
water
Important Structures in
Cytoplasm
• Ribosomes – protein synthesis
• Inclusion Bodies – globules of starch
or lipids – store nutrients
• Bacterial Chromosome – closed loop of
DNA without a membrane or proteins
(nucleoid region)
• Plasmids – smaller, separate molecules
of DNA – few genes but do give
bacteria drug resistance (R genes)
Endospores
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Some Gram-pos bacteria produce highly
resistant structures - spores
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Bacteria grow, mature and reproduce as
vegetative cells
Then the bacterial chromosome replicates
and the cell membrane grows in to seal off
a developing spore
Next, thick layers of peptidoglycan form to
protect the cell
Finally, the cell wall of the vegetative cell
disintegrates and the spore is released
•Sporulation is spore formation - DNA
+ some cytoplasm wrapped in spore
case formed by cell membrane
•Germination of spore occurs when
good environmental conditions return
– vegetative cell
Kingdom Classification
Archaeobacteria
• Have existed on earth longer than any
other living organism
• They are different from eubacteria:
– No peptidoglycan in cell wall
– Different lipids in cell membrane
– Different ribosomal RNA
– Now archaeobacteria and eubacteria are
classified as different kingdoms
Archaeobacteria
• 3 Types:
– Methanogens – rods that live in anaerobic
conditions and produce methane gas –
common in marshes and the guts of cows
and humans
– Thermoacidophiles – resistance to acid
and high temperatures – live in hot springs
and ocean vents
– Extreme Halophiles – thrive in high salt
environments (Great Salt Lake)