Download Micro Unit 4 Notes - Nutley Public Schools

Microbiology – Alcamo
Lecture: 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.
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
Gonorrhea
• Also called the "clap" or "drip," gonorrhea is a
contagious disease transmitted most often through
sexual contact with an infected person.
• Gonorrhea is caused by Neisseria gonorrhoeae, a
bacterium that can grow and multiply easily in mucus
membranes of the body.
• Symptoms:
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Greenish yellow or whitish discharge from the penis or vagina
Burning when urinating
Burning in the throat (due to oral sex)
Painful or swollen testicles (in men)
Swollen glands in the throat (due to oral sex)
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
without causing any harm.
• 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.
• 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
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Complicated structure: Filament
attached to hook-like shaft which is
inserted through cell wall and attached
to cell membrane
Flagella
Monotrichous
Lophotrichous
Amphitrichous
Peritrichous
Axial Filament
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Only spirochete
One flagella attached at both ends of
flexible spiral MO
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 MO
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 MO’s 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
•
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 have a cell wall except
mycoplasmas
• 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
•If small: thinner, G- stain reaction, not
sensitive to penicillin or lysozyme
•If MO 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
cell membrane animation
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
•
Some Gram + 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” 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)