Bacteria and Viruses We mostly don't get sick. Most often,
bacteria are keeping us well. - Bonnie Bassler
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Prokaryote Structure
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Eubacteria cell walls contain peptidoglycan, some species have
a second cell wall ( gram negative stain ) that makes them
resistant to damage. The different phylums are indicated below in
blue.
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Kingdom Archaebacteria Introns in DNA, lack peptidoglycan in
cell walls, many live in extreme environments
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Chemoheterotrophs take in organics for energy and supply of
carbon photoheterotroph s make food from sun, but need organics for
carbon photoautotrophs use light to make food and get carbon
chemoautrotrophs make food and get carbon without using the
sun
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Escherichia coli chemoheterotroph that lives in lower
intestines of mammals. It is a facultative anaerobe which means it
can survive with or without oxygen.
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Cyanobacteria this is a phylum of bacteria that obtain their
energy through photosynthesis. (photoautrophs) The slide shows
Oscillatoria, a species of cyanobacteria seen in freshwater
ponds.
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Chemoautotrophs use inorganic energy sources, like H 2 S to
synthesize food. This deep sea vent provides chemoautotrophs with
food and energy.
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Mycobacterium tuberculosis- the bacteria that causes
tuberculosis needs oxygen in order to live. The picture below shows
Mycobacterium tuberculosis embedded in lung tissue. Note the red
rods.
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Tuberculosis life cycle can be treated with antibiotics, though
a resistant strain is causing problems.
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Clostridium botulinum an obligate anaerobe, exposure to oxygen
kills this bacterium. It is found in soils and can contaminate
canned foods. Its toxins cause the disease Botulism or
lockjaw.
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A person suffering from Botulism poisoning
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Escherichia coli is a gram negative, facultative anaerobic (do
not require O 2 ) rod-shaped bacteria that is commonly found in the
lower intestines of warm-blooded animals.
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Bacterial Reproduction Binary fission most bacteria do
this
Conjugation a hollow bridge forms between two cells and some
genetic material is exchanged. This helps to increase genetic
diversity.
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Spore In unfavorable conditions a bacterium will form a thick
internal wall that encloses its DNA and a portion of its cytoplasm.
In this state the spore can survive for years until conditions
improve.
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Bacteria can decompose just about any type of organic matter.
This process helps to recycle nutrients
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Metropolitan Sewage treatment plant, Saint Paul. Treats up to
251 million gallons/day. 65 communities, 1.8 million people. Water
returned to the river is cleaner than the river water.
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Saint Paul plant is an advanced Secondary Treatment
facility.
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The dried sludge is burned in an incinerator and generates
enough electricity provide 20% of the plants power and power 1,000
homes. The new incinerator removes over 90% of all pollutants.
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Many plants have a symbiotic relationship with strains of
bacteria that can remove nitrogen from the atmosphere and make it
available for the plants and then other living things. This process
is called nitrogen fixing
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Bacteria are genetically engineered to produce human
insulin
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Bacteria is used to make cheese
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Streptomyces fradiae the bacteria that produces the antibiotic
neomycin.
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Virus Structure of HIV virus
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Lytic and Lysogenic infections with viruses.
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Chicken pox and Shingles the virus that causes chicken pox can
lie dormant in nerve cells to become active, sometimes years later.
Shingles, pictured below is very painful.
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Retroviruses store their genetic information as RNA. When
infecting a cell they produce a DNA copy of their RNA and this
becomes inserted into the hosts DNA.
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Wendell Stanley crystallized tobacco mosaic virus was
infectious and therefore viruses were not living things.
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Bacteria cause disease by either damaging cells and/or
releasing toxins that damage cells.
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Meningoccoccal Disease attack the lining (meninges) between the
brain and the skull. Produce an endotoxin that cause blood vessels
to rupture. Even with prompt antibiotics 10% die and many lose one
or more limbs.
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Vaccine a preparation of a killed or weakened bacteria or virus
that stimulates the bodys immune system to produce antibodies
against the disease.
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Antibiotics compounds that block the growth and reproduction of
bacteria. In this picture the mold penicillin notatum is producing
a compound that prevents the bacteria from growing. This compound
was the first antibiotic penicillin.
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Bacteriophages ( literally bacteria eater) are viruses that
attack and destroy bacteria.
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Bacteriophages attack specific strains of bacteria.
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Phage were used as antibacterial agents in Georgia and the US
in the 1920s and 30s. With the discovery of antibiotics they were
abandoned in the US but continued to be used in Russia.
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Bacteriophages are very specific they can attack only one
specific bacterial species. So, they would not harm beneficial
bacteria (gut flora).
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This picture shows a person being treated with phages for a
chronic year infection at a clinic in Tbilisi, Georgia
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A new company in the US, Intralytix, Inc. is marketing
bacteriophage products to control bacterial pathogens in the
environment, food processing and medical settings. This may be a
part of the answer in dealing with antibiotic resistant strains of
bacteria. In this slide bacteriophages help to clear this wound of
multi-drug resistant S. aureus.
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Viral diseases. Many Viruses infect and destroy certain cells
(i.e. Polio which destroys nerve cells). Others cause infected
cells to change their pattern of growth (plantars warts)
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Viral diseases do not respond to antibiotics. The best way to
prevent viral diseases is through a vaccine. The vaccine may be the
heat killed virus, weakened virus or a part of the capsid. In the
diagram below, a Viral antigen (surface protein) is put in vaccine.
When injected, the body makes antibodies against the specific viral
antigen.
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Dr. Jonas Salk developed the vaccine for the Polio virus in
1955. He is shown here injecting a patient with the heat killed
viral protein coat. The antibodies the girl produces will be ready
in case any real viruses invade her body. In that case they will
not get a chance to infect her.
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Sister Kenny, a rural Australian nurse, had developed a
treatment for polio. The University of Minnesota was the only
institution that would allow her to present her findings (1940).
The Sister Kenny institute continues its work today in treating
people with paralyzing diseases.
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Viroids - are plant pathogens that consist of a short stretch
(a few hundred nucleobases) of highly complementary, circular,
single-stranded RNA. They are much smaller than viruses and have no
capsid
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Prions are misfolded proteins. They transform correctly folded
proteins in the brain to match their shape just be touch. There are
no nucleic acids involved. They cause Mad Cow disease,
Creutzfeldt-Jakob Disease in humans and bovine spongiform
ecephalophthy in cows.
