Viruses, Viroids, and Prions
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Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings
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
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings
Contain DNA or RNA
Contain a protein coat
Some are enclosed by an envelope
Most viruses infect only specific types of cells
in one host
Viruses
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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
Simplexvirus
Human herpes virus
HHV-1, HHV-2, HHV-3
Retroviridae
Lentivirus
Human
immunodeficiency virus
HIV-1, HIV-2
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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
Figure 13.9
The cytopathic effect of viruses
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Virus Identification
Cytopathic effects
Serological tests
Detect antibodies against viruses in a patient.
Nucleic acids
PCR
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Multiplication of Bacteriophages (Lytic Cycle)
Attachment
Penetration
Biosynthesis
Maturation
Release
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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.
Two Possible Life Cycles
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The Lysogenic Cycle
Figure 13.12
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Bacterial Toxins Resulting from Phage Genes
Scarlet Fever – Streptococci
Botulism – Clostridium Botulinum
Cholera – Vibrio cholerae
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2
3
4
5
6
Specialized Transduction
Figure 13.13
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