Download Chapter 13 Virus Lect.

TORTORA  FUNKE  CASE
ninth edition
MICROBIOLOGY
an introduction
13
Part A
Viruses, Viroids,
and Prions
PowerPoint® Lecture Slide Presentation prepared by Christine L. Case
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings
Viruses
 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
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Viruses
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Figure 13.1
Viruses
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Figure 13.1
Virion Size
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Figure 13.1
Helical Viruses
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Figure 13.4a–b
Helical Viruses
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Figure 13.4a–b
Polyhedral Viruses
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Figure 13.2a–b
Enveloped Viruses
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Figure 13.3
Complex Viruses
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Figure 13.5a
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
 Retroviridae
 Herpesvirus
 Lentivirus
 Human herpes virus
 Human
HHV-1, HHV-2, HHV-3
immunodeficiency virus
HIV-1, HIV-2
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Figure 13.6
Viruses
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Figure 13.1
Growing Viruses
 Viruses must be
grown in living
cells.
 Bacteriophages
form plaques on
a lawn of
bacteria.
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Figure 13.6
Growing Viruses
 Animal viruses may
be grown in living
animals or in
embryonated eggs.
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Figure 13.7
Growing Viruses
 Animal and plants viruses may be grown in cell culture.
 Continuous cell lines may be maintained indefinitely.
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Figure 13.8
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
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Figure 13.9
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
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Figure 13.11, steps 1–3, 6–7
4
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Figure 13.11, steps 4–5, 8
One-Step Growth Curve
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Figure 13.10
 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
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Figure 13.12
Specialized Transduction
2
3
4
5
6
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Figure 13.13
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
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