PowerPoint Presentation · PPT file · Web view · 2014-09-11Viruses:...
Transcript of PowerPoint Presentation · PPT file · Web view · 2014-09-11Viruses:...
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Viruses: Morphology and Bacteriophage Life Cycle
Figure 13.1
What is a Virus and How is it Built?•Obligate intracellular parasites
•Morphology of a Virion•Size (1/1000 to 1/4 size of bacterium)•Composition
•RNA vs DNA•Capsid, envelope, spikes
•Shapes•helical, polyhedral (isometric) , complex
•Host ranges and grouping of viruses•Bacterial, plant, animal viruses
•Propagation and study of viruses•Bacteriophage plaques on a lawn•Animal virus propagation•Identifying viruses
Bacterial Virus Life Cycles (DNA viruses)•Lytic Cycle (e.g. T4 bacteriophage)
•Attachment•Penetration/Entry•Biosynthesis•Assembly•Lysis/Release
•Lysogenic Life CycleViruses cannot reproduce outside of a cell. They are extremely small and come in three different shapes. They are very specific for their hosts. In the lytic cycle of bacteriophages, they enter, reproduce, and leave.
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Viruses
Figure 13.1
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Helical Viruses
Figure 13.4a, b
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Polyhedral (Isometric) Viruses
Figure 13.2a, b
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Some Viruses Have a Phospholipid Envelope
Membrane proteinsform “spikes” that stick out from membrane
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Complex Viruses
Figure 13.5a
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Viral Taxonomy
• “Family” names end in -viridae• “Genus” names end in -virus • Viral species: A group of viruses sharing the same
genetic information and ecological niche (host). Common names are used for species
• Subspecies are designated by a number
• Herpesviridae• Herpesvirus• Human herpes
virus 1, HHV 2, HHV 3
• Retroviridae• Lentivirus• Human
Immunodeficiency Virus 1, HIV 2
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Viruses: Morphology and Bacteriophage Life Cycle
Figure 13.1
What is a Virus and How is it Built?•Obligate intracellular parasites
•Morphology of a Virion•Size (1/1000 to 1/4 size of bacterium)•Composition
•RNA vs DNA•Capsid, envelope, spikes
•Shapes•helical, polyhedral, complex
•Host ranges and grouping of viruses•Bacterial, plant, animal viruses
•Propagation and study of viruses•Bacteriophage plaques on a lawn•Animal virus propagation•Identifying viruses
Bacterial Virus Life Cycles (DNA viruses)•Lytic Cycle (e.g. T4 bacteriophage)
•Attachment•Penetration/Entry•Biosynthesis•Assembly•Lysis/Release
Viruses cannot reproduce outside of a cell. They are extremely small and come in three different shapes. They are very specific for their hosts. In the lytic cycle of bacteriophages, they enter, reproduce, and leave.
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Growing Viruses
• Viruses must be grown in living cells.
• Bacteriophages form plaques on a lawn of bacteria.
Figure 13.6
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• Animal viruses may be grown in living animals, or in embryonated eggs, or in tissue culture
Growing Viruses
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Growing Viruses
• Animal and plants viruses may be grown in cell culture.• Continuous cell lines may be maintained
indefinitely.
Figure 13.8
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• Cytopathic effects• Serological tests
• Detect antibodies against viruses in a patient• Use antibodies to identify viruses in neutralization
tests, viral hemagglutination, and Western blot• Nucleic acids
• RFLPs (DNA fingerprint)• PCR (selectively amplifying and detecting key
sequences)
Virus Identification
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Viruses: Morphology and Bacteriophage Life Cycle
Figure 13.1
What is a Virus and How is it Built?•Obligate intracellular parasites
•Morphology of a Virion•Size (1/1000 to 1/4 size of bacterium)•Composition
•RNA vs DNA•Capsid, envelope, spikes
•Shapes•helical, polyhedral, complex
•Host ranges and grouping of viruses•Bacterial, plant, animal viruses
•Propagation and study of viruses•Bacteriophage plaques on a lawn•Animal virus propagation•Identifying viruses
Bacterial Virus Life Cycles (DNA viruses)•Lytic Cycle (e.g. T4 bacteriophage)
•Attachment•Penetration/Entry•Biosynthesis•Assembly•Lysis/Release
Viruses cannot reproduce outside of a cell. They are extremely small and come in three different shapes. They are very specific for their hosts. In the lytic cycle of bacteriophages, they enter, reproduce, and leave.
![Page 14: PowerPoint Presentation · PPT file · Web view · 2014-09-11Viruses: Morphology and Bacteriophage Life Cycle What is a Virus and How is it Built? Obligate intracellular parasites](https://reader035.fdocuments.net/reader035/viewer/2022062907/5a9ee1d57f8b9a71178bfe9d/html5/thumbnails/14.jpg)
Figure 13.10.1
Attachment:Phage attaches to host cell.
Penetration:Phage pnetrates host cell and injects its DNA.
Biosynthesis: Transcription/Translation andViral chromosome replication
1
2
3
Bacterial cell wall
Bacterial chromosome
Capsid DNA
Capsid
SheathTail fiberBase platePinCell wall
Tail
Plasma membrane
Sheath contracted
Tail core
Lytic Lifecycle of a Bacteriophage I
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Figure 13.10.2
4 Maturation/Assembly:Viral components are assembled into virions.
Tail
5 Release:Host cell lyses and new virions are released.
DNA
Capsid
Tail fibers
Lytic Lifecycle of a Bacteriophage II
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Lytic Life Cycle Overall
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The Lytic and Lysogenic Cycles
Figure 13.12
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Viruses: Morphology and Bacteriophage Life Cycle
Figure 13.1
What is a Virus and How is it Built?•Obligate intracellular parasites
•Morphology of a Virion•Size (1/1000 to 1/4 size of bacterium)•Composition
•RNA vs DNA•Capsid, envelope, spikes
•Shapes•helical, polyhedral, complex
•Host ranges and grouping of viruses•Bacterial, plant, animal viruses
•Propagation and study of viruses•Bacteriophage plaques on a lawn•Animal virus propagation•Identifying viruses
Bacterial Virus Life Cycles (DNA viruses)•Lytic Cycle (e.g. T4 bacteriophage)
•Attachment•Penetration/Entry•Biosynthesis•Assembly•Lysis/Release
•Lysogenic Life CycleViruses cannot reproduce outside of a cell. They are extremely small and come in three different shapes. They are very specific for their hosts. In the lytic cycle of bacteriophages, they enter, reproduce, and leave.