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1
CHAPTER 4
VIRUSES
MONERA
• STRUCTURE
AND SHAPE
• CLASSIFICATION
• REPRODUCTION
• RETROVIRUS
• ORIGIN OF
VIRSUSES
• CLASSIFICATION
• STRUCTURE
• ECOLOGY/
ADAPTATION
• REPRODUCTION
• ECONOMIC
IMPORTANCE
• Bacteria Testing
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Structure and Shape of viruses
• Don’t possess life functions
• Composed of Protein coat and Genetic
materials ( DNA or RNA)
• Most are spherical or other geometric
form
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Shape of viruses
• Many are spherical with
projections
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More Virus shapes
Filamentous virus
Ebola
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Complex Virus Structures
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HIV MODEL
RNA
Inner protein
Core Protein
Coat
Enzymes
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Virus slides
1- Influenza virus
2- Polio virus
3- Tobacco Mosaic virus
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Virus Sizes
• With electron microscopy the level of resolution is
5nm (1nm = 10-9 meters). To put this into some
kind of perspective:
• an atom is about 0.2-0.3 nm in diameter
• DNA is about 2nm in diameter. A small virus
• parvovirus has a diameter of about 25nm. A large
virus (e.g.
• poxviruses) have a diameter of up to 300nm.
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Classification of Viruses
• Grouped by the type of genetic material
they have
– Single strand of DNA
– Double strands of DNA
– Single strand of RNA
– Double Strands of RNA
• Shape and size
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Virus Families
Poxviridae (pox viruses)
Parvoviridae
Reoviridae
Picornaviridae (Hepatitis A virus, footand-mouth disease virus)
Togaviridae (Rubella virus)
Flaviviridae (Hepatitis C virus, yellow
fever virus)
Rhabdoviridae
Bunyaviridae (Hantaan virus)
Herpesviridae (Human Herpes Simplex
Viruses 1&2, VZV, Human
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Virus Families continued
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Adenoviridae
Papovaviridae (Papillomaviruses)
Hepadnaviridae (Hepatitis B virus)
Caliciviridae
Arenaviridae
* Paramyxoviridae (Measles virus)
* Orthomyxoviridae (Influenza viruses AC)
• * Filoviridae (Ebola virus)
• * Retroviridae (HIV-1&2, HTLV-1)
• * Astroviridae
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Viral Reproductions
• Since viruses are nonliving they
must use a host for reproduction.
The host provided all the
material and energy to replicate
itself.
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Viral Reproductions-2
• Viruses are very specific in which
types of cell they require as host.
This is why it is very difficult
(but not impossible)to get a virus
infection from an animal.
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Viral Reproductions-3
• Two types of reproductive cycles
–Lytic cycle
–Lysogenic cycle
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Lytic Cycle
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Attachments
Entry ( injection / endocytosis )
DNA or RNA replication
Assembly New protein coat added
Releasing new virus
– Lysis
– Budding
– Cell membrane channels
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Replication steps
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Lysogenic Cycle see page 75
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Attachment
Entry
Provirus formation
Cell Division
Trigger
Lytic cycle
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Retrovirus
• The most complex RNA viruses
• During injection of their RNA they
also inject a special enzyme that help
in the reverse transcriptase
• HIV is such a virus
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ORIGIN OF VIRUSES
• The theory is that viruses originated
from cells who DNA or RNA some
how escaped a developed a way to
reproduce as parasites.
• This would indicate that new viruses
could be continually being made.
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Monera (Bacteria)
• Archaebacteria - ancient bacteria
that live in extreme enviroments.
– Oxygen free environments
– salt water environments
– hot acidic waters
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Life on Mars
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Eubacteria- Heterotrophs
• Heterotrophs- decomposers
• Eubacteria - Chemosynthetic
• Eubacteria- Photosynthetic
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Bacteria structures
• Shapes
– coccus- round
– bacillus- rod shape
– spirallus- cork screw shape
• Arrangements
– diplo– staphylo– strepto-
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Shapes of Bacteria
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Coccus - Round shape
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Bacillus- Rod Shape
Bacillus 2
E. Coli sem x1815
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E.coli
Sem x49,440
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Streptomyces
sem x 5,510
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Spirallus bacteria
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Naming of Bacteria
• Names are a combinations of the
shape and the cluster arrangements.
– Example
–diplococcus
–streptococcus
–staphylbaccillus
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A typical bacteria structure 1
• Prokaryotes- Lack a membrane bound
nucleus.
• Cell wall- Different chemical
composition than plants- complex
polysaccharide (not found in eukaryotes)
• Plant cell walls contain cellulose.
• See Transparency # 44
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Structures-2
• Capsule- slimy material that covers the
cell wall. Protects the bacteria.
EX. Capsule protects the cell from the
white blood cells and antibodies
produced by animal cells.
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Structures-3
• Cell membrane- located just inside the
cell wall. Prokaryotes lack organelles.
All reactions take place in the folds of
the cell membrane.
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Structure continued 2
• Cytoplasm- contains ribosome (synthesize
proteins). If bacteria carry out photosynthesis
chlorophyll is contained here.
• Hereditary material (DNA)- Lack a "true"
nucleus. DNA is circular. Found in the
nucleolid. Plamids are smaller segments of
DNA.
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Structures -3
• 6.Endospores- Formed within the
cytoplasm. Contain DNA and a small
amount of cytoplasm. Form when
conditions are unfavorable. Allows the
bacteria to remain dormant. When
conditions become favorable the bacteria
will grow again. Developed this trait for
survival
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Protection from Osmotic rupture
• Like most living things the concentration of
water and other liquids is higher outside the
organism then inside
• Most bacteria have a thick cell wall
composed of sugar molecules linked with
amino acids.
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Penicillin- Bacteria Killer?
• Penicillin kills bacteria by interfering with
the amino acids that link the sugars together
in the cell wall
• This rupturing of the wall allows water to
rush in lysing the cell
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Ecology and Adaptations
• Obligate aerobes bacteria require oxygen
• Obligate anaerobes live in an oxygen free
environment. - oxygen will kill them.
• Endospores are formed by some bacteria
when conditions become harmful to them
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Reproductions
• Binary fission- asexual process - bacteria
will simply undergo mitosis
• Sexual reproduction - Chromosomes are
exchanged from one bacteria to another
through the Pili
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Reproduction
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Rod shape bacteria with Pilus
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SEM of Pili
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Economic Importance
• Nitrogen fixation - all organism need
nitrogen to construct things like
protein, DNA, RNA and ATP.
• Nitrogen fixation - occurs in some
bacteria that are able to get nitrogen
from the air (N2) and convert it to NH3
or NO2, NO3
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Nitrogen Fixing nodules
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Economic Importance 2
• Bacteria cause organic material to
decay. This allows for the recycling of
nutrients.
• Some bacteria use fermentation which
makes a variety of molecules with
distinctive flavors and aromas- Yogurt,
cheese, vinegar.
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Why to we culture bacteria?
• to study them in more detail
• to study or improve strains of bacteria.
• to identify which bacterium has
infected you and therefore what
treatment to begin.
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How Bacteria are cultured?
• Life forms require certain foods, water
and temperatures to exist bacteria are
no exception.
• Each type of bacteria prefers either
sugars, starch, fats or proteins. So by
providing a certain nutrient you will
encourage a specific type of bacteria to
grow.
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How Bacteria are cultured? -2
• Temperature should be 20 C to 37 C
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Inoculation
• Adding bacteria to
a culture dish is
called inoculation
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Inoculation results
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Inoculation results 2
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Inoculation results 3
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Culture Results
• By Studying pure culture plates of a
bacterial species, and observing the
texture, aroma, color, growth pattern,
height of the growth, and other
physical characteristics of the colonies,
you can learn a lot about the specimen.
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Testing Bacteria
• One way to determine how to treat a
bacteria is to determine the type of cell
wall it has.
– Thick wall usually indicate a Gram
positive type
– Thin wall usually indicate a Gram
negative type
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Gram Negative test
• It was found that thick wall bacteria
will stain differently than those that
have thin wall.
• The Gram negative test uses a process
to stain bacteria.
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Gram Positive
• They are usually Coccus and Bacillus
in shape
• Most are harmless to people and are
used for their fermentation process to
make foods.
• Examples of common Gram-positive
cells include Staphylococcus
aureusand Streptococcus cremoris, a
bacterium used in dairy production.
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Gram Negative
• These bacteria are more harmful then
helpful
• Afflicted individuals are usually
treated with streptomycin or
erythromycin.