MICROORGANISMS: Viruses,
Prions, Archaea
What do Archaea and Bacteria have in
common?
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Single celled
Microscopic
No membrane bound nucleus
Both essential to all other life on earth
What about viruses? Living or non-living?
• Can they perform the functions of independent
cells? Do they make their own proteins, have
waste disposal?
• Are they made of cells?
• Do they have genetic material of their own? If so
how many genes are there?
• Can they replicate?
• Viruses are non-cellular replicating entities that
invade living cells to carry out their replication.
• Because viruses cannot carry out replication by
themselves, most scientists do not classify them as
living things.
• The Human Immunodeficiency virus (HIV), which
causes AIDS, has two structures common to almost
all viruses:
– genetic material and
– a protein coat, called a capsid, surrounding this
material.
– HIV also has one other structural element that many
viruses possess: a fatty membrane, called an
envelope, which surrounds the capsid.
Viruses cause a host of human illness. New
viruses harmful to human beings periodically
come along by means of viruses that infect
other animals mutating and then “jumping” to
human hosts.
All forms of life are vulnerable to viral
infections.
Viral Life Cycle
1. They insert their genetic material inside a
“host” cell;
2. Turn out viral component parts, construct
new virus clones or “particles” from these
parts;
3. Move the new particles out of the cell, at
which point the particles go on to infect
more cells.
Viruses are noncellular, replicating
entities that must
invade a host to carry
out replication
T4 Virus
(bacteriaphage)
HIV
PRIONS
They are not viruses?
• Prions are small, proteinaceous infectious particles
that resist inactivation by procedures which affect
nucleic acids.
• Prions are pathogenic variants of proteins that are
naturally produced in nerve cells and certain other
cells
• No detectable nucleic acids of any kind and no viruslike particles have been associated with prions.
• But the rogue prions seem to force the normal
proteins to change shape.
A prion is an abnormal, transmissible agent that is able to
induce abnormal folding of normal cellular prion
proteins in the brain.
It leads to brain damage and the characteristics signs and
symptoms of the disease.
Prion diseases are usually rapidly progressive and always
fatal.
A family of rare progressive neurodegenerative disorders
that affect both humans and animals.
Human Prion Diseases
Creutzfeldt-Jakob Disease (CJD)
Gerstmann-Straussler-Scheinker Syndrome
Fatal Familial Insomnia
Kuru
Animal Prion Diseases
Bovine Spongiform Encephalopathy (BSE) (Mad Cow
Disease)
Chronic Wasting Disease (CWD)
Scrapie
Transmissible mink encephalopathy
Feline spongiform encephalopathy
ARCHAEA
What makes Archaea different from
Bacteria?
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Simplest form of life
Likely the oldest form of life
Live in extreme environments; extremeophiles
Several subgroups: we will cover 3 of them
Different Cell wall construction
Thermoacidophiles
80-9- degrees C and pH2
Image of the geothermal site
at Pisciarelli (Napoli, Italy).
Acidic sulphur fumes rise from
a fissure in the rocks. The bright
green biomat is populated by a
diverse assemblage of
eukaryotic thermoacidophiles,
the Cyanidiales
Extreme halophiles- salt lovers, live in salt
concetrations of 10-12% salt lake, dead sea
• Halophiles have turned
the land that surrounds
the Great Salt Lake in
Utah a reddish color.
This happens to the
land after flood water
spreads onto the land.
Methanogens- strict anaerobes. Produce
methane gas.
• Methanogens thrive in extreme environments such
as geothermal springs.
• Sewage treatment plants and intestinal tracts of
animals (example cows) Dumps smell is from
adding methanogens to decompose the garbage
and produces methane gas, that’s what you smell.
Often see metal tubes to pipe gas out so doesn’t
explode. Can collect methane
• Francis H. Chapelle, of the
US Geological Survey in
Columbia, South Carolina,
and colleagues analyzed
DNA sequences recovered
from the waters of Lidy Hot
Springs in Idaho and found
that more than 90 percent
of the organisms were
methanogens. This is the
highest-known
concentration of such
microbes discovered so far
in any one place