Post on 30-Dec-2015
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CHAPTER 4VIRUSES 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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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
11Virus Families• Poxviridae (pox viruses)• Parvoviridae• Reoviridae• Picornaviridae (Hepatitis A virus, foot-and-
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• Adenoviridae• Papovaviridae (Papillomaviruses)• Hepadnaviridae (Hepatitis B virus)• Caliciviridae• Arenaviridae• * Paramyxoviridae (Measles virus)• * Orthomyxoviridae (Influenza viruses
A-C)• * 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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Lytic Cycle• 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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Lysogenic Cycle see page 75
• 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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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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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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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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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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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.