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PowerPoint® Lecture Slide Presentation prepared by Christine L. Case
M I C R O B I O L O G Ya n i n t r o d u c t i o n
ninth edition TORTORA FUNKE CASE
Part A13Viruses, Viroids,
and Prions
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Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings
Contain DNA or RNA –sDNA, dDNA, sRNA, dRNA
Contain a protein coat
Some are enclosed by an envelope
Some viruses have spikes
Most viruses infect only specific types of cells
in one host
Host range is determined by specific host attachment
sites and cellular factors
Viruses
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Viruses
Figure 13.1
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Viruses
Figure 13.1
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Virion Size
Figure 13.1
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Helical Viruses
Figure 13.4a–b
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Helical Viruses
Figure 13.4a–b
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Polyhedral Viruses
Figure 13.2a–b
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Enveloped Viruses
Figure 13.3
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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.
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Viral Taxonomy
Herpesviridae
Herpesvirus
Human herpes virus
HHV-1, HHV-2, HHV-3
Retroviridae
Lentivirus
Human
immunodeficiency virus
HIV-1, HIV-2
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Figure 13.6
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Viruses
Figure 13.1
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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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Growing Viruses
Animal viruses may
be grown in living
animals or in
embryonated eggs.
Figure 13.7
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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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Virus Identification
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
PCR
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Virus Identification
Figure 13.9
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Multiplication of Bacteriophages (Lytic Cycle)
Attachment: Phage attaches by tail fibers to host cell.
Penetration: Phage lysozyme opens cell wall, tail
sheath contracts to force tail core and DNA into cell.
Biosynthesis: Production of phage DNA and proteins.
Maturation: Assembly of phage particles.
Release: Phage lysozyme breaks cell wall.
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1
2
3
Figure 13.11, steps 1–3, 6–7
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4
Figure 13.11, steps 4–5, 8
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One-Step Growth Curve
Figure 13.10
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Lytic cycle: Phage causes lysis and death of host cell.
Lysogenic cycle: Prophage DNA incorporated in host
DNA.
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The Lysogenic Cycle
Figure 13.12
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2
3
4
5
6
Specialized Transduction
Figure 13.13
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Multiplication of Animal viruses
Attachment: Viruses attach to cell membrane.
Penetration by endocytosis or fusion.
Uncoating by viral or host enzymes.
Biosynthesis: Production of nucleic acid and proteins.
Maturation: Nucleic acid and capsid proteins assemble.
Release by budding (enveloped viruses) or rupture.
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Multiplication of Animal viruses
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Multiplication of Animal viruses
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Multiplication of Animal viruses
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Multiplication of Animal viruses
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PERSISTANCE VS. LATENT INFECTIONSs
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PERSISTANCE VS. LATENT INFECTIONSs
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PRIONS
Infectious Proteins
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VIROIDS
Infectionus RNA
Plant diseases so far
