-4- micro Virology
Terms
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- Charles Chamberland
- Discovered porcelain filters used to filter (remove) bacteria.
- Dmitri Ivanovsky
- Discovered that some filtrates remained infectious???
- Martinus Beijerinck
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"Contagium vivium fluidium"
(Contagious living fluid)
Later coined the name virus
(meaning poison or venom) -
isolate
propogate
observe and analyze was not available. - The lack of technology needed to: ________,_________, and ________________________ was lacking prior to the 1930s.
- Wendell stanley
-
Crystallized the first virus (TMV)
Consisted of protein and RNA
Viruses first observed with an electron microscope. - Mendel's Particles
-
Gregor mendel
Certain inherited traits seem to be passed from parent to offspring as discrete hereditary "particles". - Hershey and Chase
- Discovered the genetic material of some VIRUSES was DNA
-
1. Contain a single type of nucleic acid, either DNA or RNA.
2. Contain a protein coat (capsid) around the nucleic acid.
3. Some have a envelope (plasma membrane) around the protein coat.
4. Multiply inside living cells (Viruses can't syn - What are the general characteristics and structure of viruses?
-
capsomeres
Immunogenic -
The general characteristic and structure of a virus consists of protein subunits called _________.
Is Antigenic/___________ (stimulates antibody production) - capsid
-
(Characteristic and structure of a virus)
Contain a protein coat (_______) around the nucleic acid. - envelope (plasma membrane)
- Some viruses have an __________ around the protein coat.
- synthesize
- (Characteristic and structure of a virus)Multiply inside living cells (viruses can't _________ proteins or generate ATP).
- host
- Viruses take over the metabolic activity of _____ cells.
-
clinical
replication - Important for _________ control: Difficult to disrupt viral __________ without interfering with host cell function.
- through an electron microscope.
- What is the only way you can see a virus?
- 20-14,000 nm
- What is the size of a virus?
- Shapes of viruses
-
Helical/Spiral
Icosahedral (20 sided polyhedron)
Enveloped
Complex - heat
- Most viruses are destroyed by >60' C, 140'F
- Cold
-
This environmental effect has little effect on viruses.
They survive in -76' C for over 1 year. - Desiccation
- This environmental effect tolerate drying on viruses.
- pH
- This environmental effect can tolerate from ranges ~5-9.
- Disinfectants
-
This environmental effect are mostly ineffective on viruses.
Alcohol can destroy lipid enveloped viruses - Oxidizing agents
- What environmental effect is mostly effective, and has to do with Hydrogen Peroxide, chlorine, and iodine.
- UV light
- What environment effect damages nucleic acids on viruses?
-
1. Living animals and plants
2. Embryonic eggs
3. Tissue/Cell culture
4. Bacterial culture - What is required for cultivation of viruses? (4)
- Embryonic eggs
- Virus is injected into embryonic tissues and membranes.
- Tissue/Cell culture
-
Cells in solution that provides : nutrients, proper osmotic pressure, pH, etc.
include:
primary cell & embryonic cell lines
Continuous/immortal cell lines - primary cell & embryonic cell lines
- Grow for a short time in vitro.
- Continuous/immortal cell lines
- Can be maintained in vitro indefinitely.
-
1. Attachment/Adsorption
2. Penetration
3. Biosynthesis
4. Maturation/Assembly
5. Release/Lysis - What are the 5 phases of T-even bacteriophage Lytic cycle?
- Attachment/Adsorption
-
A phase in T-even bacteriophage lytic cycle
Phage tail fibers attach to specific receptors on bacteria. - Penetration
-
A phase in T-even bacteriophage lytic cycle
Phage release enzyme -> lysosome dissolves part of the bacteria cell wall. Tail sheath contracts and drives phage core through the cell wall and injects DNA. - Biosynthesis
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A phase in T-even bacteriophage lytic cycle
Viral DNA takes over the machinery of the host cell and begins producing viral DNA and structural components. - Maturation/Assembly
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A phase in T-even bacteriophage lytic cycle
Phage DNA assembles into complete viruses. - Release/Lysis
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A phase in T-even bacteriophage lytic cycle
Phage lysosome breaks down bacterial cell wall and multiplied phages are released. - "burst time"
- The time from adsorption to release.
- "burst size"
- The average number of virons released by a cell. (50-200 virons for T-even phage).
- Lysogeny
- Viral DNA is incorporated into the host DNA without causing lysis of the host cell.
-
Lysogenic cell
repressor protein. - A cell containing a prophage (provirus). Prophage genes are repressed by a _________ _______.
- Latency
- Ability to remain in host cells for long periods.
-
Induction/Excision
Specialized Transduction - What are the 2 phage conversions?
- Induction/Excision
-
Certain environmental factors may cause a prophage to revert to the lytic cycle.
e.g. UV light or certain chemicals. - Specialized Transduction
- When a prophage is excised from the host chromosome it can take with it adjacent DNA from the bacterial chromosome.
- Animal viruses
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Attachment
Penetration occurs by endocytosis
Uncoating by viral or host cell enzymes.
Biosynthesis
Maturation and Release (budding) - Latent viral infections
-
Virus remains in asymptomatic host cell for long periods. Reactivated by: fever, UV light, stress, trama, hormonal changes, and repair mechanisms in the cell.
eg. cold sores and shingles -
Wilhelm Ellerman & Olaf Bang
F. Peyton Rous
Michael Bishop and Harold Varmus - Who worked on viruses and cancer?
- Wilhelm Ellerman & Olaf Bang
- Found that leukemia could be transferred to healthy chickens by cell-free filtrates containing viruses.
- F. Peyton Rous
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Found that chicken sarcoma (cancer of conn. tissue) similarly transmitted.
Oncogenes (cancergenes) - Oncogenes (cancergenes)
- Genes that can cause a normal cell to be transformed into a malignant cell.
- Michael Bishop and Harold Varmus
-
Won noble prize
Cancer-producing genes carried by viruses are derived from the animal cells genome. - Proto-oncogenes
- Normally direct synthesis of products for cell growth and development. When a virus containing an oncogene is introduced into a cell, the cell may be unable to regulate synthesis of the virus's oncogene. The excess product may result in uncontrolled cell division.