Download Chapter 13 Powerpoint lecture

TORTORA • FUNKE
• CASE
Microbiology
Differentiate between a
virus and a bacterium.
AN INTRODUCTION
EIGHTH EDITION
B.E Pruitt & Jane J. Stein
Viruses may be regarded
as exceptionally
complex aggregations of
nonliving chemicals OR
exceptionally simple
living microbes.
Chapter 13
Viruses, Viroids, and Prions
PowerPoint® Lecture Slide Presentation prepared by Christine L. Case
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Viruses (range from 20 to 1000 nm)
Viruses
nm = 10-9 m
• Viruses contain DNA or RNA
• And a protein coat
• Some are enclosed by an envelope (lipids,
proteins, and carbohydrates)
• 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
• Obligatory intracellular parasites, causing
synthesis of specialized elements that transfer
viral nucleic acid to other cells.
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Nonenveloped Polyhedral Viruses
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 13.1
Enveloped Helical Virus
Describe the chemical composition and physical structure of an enveloped and
a nonenveloped virus.
Virion = complete, fully developed viral particle of nucleic acid
surrounded by a coat
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 13.2a, b
Viruses contain either DNA or RNA, but never both. Nucleic acid may
be single or double stranded, linear or circular, or divided into several
separate
Copyright © 2004 molecules.
Pearson Education, Inc., publishing as Benjamin Cummings
1
Helical Viruses
Complex Viruses
• Capsid – protein
coat surrounding
nucleic acid
• Composed of
capsomeres, single
or multiple proteins
Helical viruses look like long or coiled threads.
Their capsids are hollow cylinders surrounding the DNA/RNA.
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 13.4a, b
Viral Taxonomy
Define viral species.
• Classification based on type of nucleic acid, replication,
and morphology.
• 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
Figure 13.5a
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Viral Taxonomy
Give an example of a family, genus, and common name for a virus.
• Herpesviridae
• Retroviridae
• Herpesvirus
• Lentivirus
• Human herpes
virus 1, HHV 2,
HHV 3
• Human
Immunodeficiency Virus
1, HIV 2
• Subspecies are designated by a number
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
2
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Growing Viruses
Growing Viruses
Describe how animal viruses are cultured.
Describe how bacteriophages are cultured.
• Viruses must be
grown in living
host cells.
• Viruses must be
grown in living
cells.
• Animal viruses
may be grown in
living animals or
in embryonated
eggs.
• Bacteriophages
form plaques
(clearings) on a
lawn of bacteria.
• Easiest to grow
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 13.6
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 13.7
Cytopathic effect of viruses
Growing Viruses
• Animal and plants viruses may be grown in cell
culture.
• Continuous cell lines may be maintained
indefinitely.
• Cytopathic effects due to viral growth
Uninfected mouse cells form monolayer (left). Infected cells 24
hours later pile up and round up (right).
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 13.8
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 13.9
3
Virus Identification
Multiplication of Bacteriophages (Lytic Cycle)
List three techniques that are used to identify viruses.
• Serological tests
• Detect antibodies against viruses in a patient
• Use antibodies to identify viruses in neutralization
tests, viral hemagglutination, and Western blot
• Nucleic acids
• 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
• RFLPs – restriction fragment length polymorphisms
• PCR – polymerase chain reaction (used to identify
West Nile virus in U.S. in 1999)
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Lytic cycle of T-even bacteriophage
Bacterial
cell wall
Bacterial
chromosome
Capsid
Lytic cycle of T-even bacteriophage
Burst time is generally about 20 – 40 minutes after phage absorption.
Burst size ranges from 50 to 200 new phage cells.
DNA
Capsid
Tail
DNA
Sheath
Tail fiber
1 Attachment:
Base plate
Pin
Cell wall
Phage attaches
to host cell.
Tail
Plasma membrane
4 Maturation:
Viral components
are assembled into
virions.
Capsid
2 Penetration:
Phage penetrates
host cell and
injects its DNA.
Sheath contracted
5 Release:
Host cell lyses and
new virions are
released.
Tail core
Tail fibers
3 Merozoites released
into bloodstream
from liver may
infect new red
blood cells
Describe the lytic cycle of T-even bacteriophages.
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 13.10.1
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 13.10.2
One-step Growth Curve for bacteriophage
• Lytic cycle
Phage causes lysis and death of
host cell
• Lysogenic cycle
Prophage DNA incorporated in
host DNA
During biosynthesis and maturation, separate components of DNA
and protein may be detected in the host cell.
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 13.11
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
4
The Lysogenic Cycle – bacteriophage lambda in E.coli
Describe the lysogenic cycle of bacteriophage lambda.
Specialized Transduction
Prophage
gal gene
Bacterial DNA
1 Prophage exists in galactose-using host
(containing the gal gene).
Galactose-positive
donor cell
gal gene
2 Phage genome excises, carrying
with it the adjacent gal gene from
the host.
3 Phage matures and cell lyses, releasing
phage carrying gal gene.
gal gene
4 Phage infects a cell that cannot utilize
galactose (lacking gal gene).
Galactose-negative
recipient cell
5 Along with the prophage, the bacterial gal
gene becomes integrated into the new
host’s DNA.
6 Lysogenic cell can now metabolize
galactose.
Galactose-positive recombinant cell
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 13.12
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 13.13
Multiplication of Animal viruses
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
• Attachment
Viruses attaches 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
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Attachment, Penetration, and Uncoating
Compare and contrast the multiplication cycle of DNA- and RNA-containing
animal viruses.
Entry of herpes simplex virus into an animal cell.
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 13.14
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
5
Multiplication of Papovarius, a DNA-containing Virus
Papovavirus
1 Virion attaches to host cell
7 Virions are released
Host cell
DNA
Capsid
2 Virion penetrates
DNA
cell and its DNA is
uncoated
Cytoplasm
6 Virions mature
Capsid proteins
mRNA
5 Late translation;
capsid proteins
are synthesized
4 Late transcription;
DNA is replicated
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
3 Early transcription and
translation; enzymes are
synthesized
DNA-containing animal viruses: individual capsomeres visible
Figure 13.15
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Pathways of Multiplication for RNA-Containing Viruses
DNA-containing animal viruses: envelop around this
herpes simplex virus broken (fried egg appearance)
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 13.17
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Multiplication & Inheritance in a Retrovirus
Capsid
Reverse
transcriptase
DNA
Virus
Two identical + stands of RNA
1 Retrovirus penetrates
host cell.
Host
cell
DNA of one of the host
cell’s chromosomes
5 Mature
retrovirus
leaves host
cell, acquiring
an envelope as
it buds out.
Identical
strands of
RNA
Viral proteins
RNA
RNA-containing animal viruses: rubella (left), mouse mammary
tumor virus (right).
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Reverse
transcriptase
Viral RNA
4 Transcription of the
provirus may also occur,
producing RNA for new
retrovirus genomes and
RNA that codes for the
retrovirus capsid and
envelope proteins.
Provirus
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
2 Virion penetrates
cell and its DNA is
uncoated
3 The new viral DNA is
transported into the host
cell’s nucleus and integrated
as a provirus. The provirus
may divide indefinitely with
the host cell DNA.
Figure 13.19
6
Release of an enveloped virus by budding
Most enveloped viruses take
part of host’s plasma
membrane for their envelope.
Cancer
Define oncogene and transformed cell.
• Activated oncogenes transform normal cells into
cancerous cells. (malignant transformation)
• Transformed cells have increased growth, loss of
contact inhibition, tumor specific transplant and T
antigens, chromosome abnormalities, can produce
tumors when injected into susceptible animals.
• Several DNA viruses and retroviruses are oncogenic.
• The genetic material of oncogenic viruses becomes
integrated into the host cell's DNA.
Figure 13.20
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Oncogenic Viruses
Discuss the relationship of DNA- and RNA-containing viruses to cancer.
Provide an example of a latent viral infection.
• Latent Viral Infections
• Oncogenic DNA Viruses
• Adenoviridae
• Oncogenic RNA viruses
• Retroviridae
• Papovaviridae
• Viral RNA is
transcribed to DNA
which can integrate
into host DNA
• Hepadnaviridae
• HTLV 1
• Heresviridae
• Poxviridae
• HTLV 2
•Retroviruses carry reverse transcriptase which
allows RNA to DNA, permitting oncogenic properties
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
• Virus remains in asymptomatic host cell for long
periods
• Cold sores, shingles
• Persistent Viral Infections
• Disease processes occurs over a long period,
generally fatal
• Subacute sclerosing panencephalitis (measles
virus)
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Prions
Differentiate between persistant viral infections and latent viral infections.
Discuss how a protein can be infectious.
• Infectious proteins first discovered in 1980’s
• Inherited and transmissible by ingestion, transplant, &
surgical instruments
• Spongiform encephalopathies: Sheep scrapie,
Creutzfeldt-Jakob disease, Gerstmann-SträusslerScheinker syndrome, fatal familial insomnia, mad cow
disease
• PrPC, normal cellular prion protein, on cell surface
•Persistent viral infections are caused by conventional
viruses, occur over a long period, generally fatal.
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
• PrPSc, scrapie protein, accumulate in brain cells
forming plaques
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
7
Prions
Some Plant Viruses
How a protein can be infectious: if an abnormal prion protein
enters cell, it changes a normal prion to PrPSc, which changes
another normal PrP (accumulation of abnormal PrPSc)
Name a virus that causes a plant disease.
PrPSc
PrPc
2
1
3
4
Lysosome
Endosome
5
6
7
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
8
Figure 13.21
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Table 13.6
Linear and circular potato spindle tuber viroid
Differentiate between virus, viroid, and prion.
• Plant Viruses
Virus Families
• Plant viruses
enter through
wounds or via
insects
• Single-stranded DNA,
nonenveloped viruses
• Viroids
• Parvoviridae
• Viroids are
infectious RNA;
potato spindle
tuber disease
• Human parvovirus
• Fifth disease
• Anemia in
immunocompromised
patients
• Prion = infectious
protein
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 13.22
Double-stranded DNA, nonenveloped viruses
• Mastadenovirus
• Respiratory
infections in
humans
• Tumors in animals
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Double-stranded DNA, nonenveloped viruses
• Papillomavirus
(human wart virus)
• Polyomavirus
• Cause tumors,
some cause
cancer
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
8
Double-stranded DNA, nonenveloped viruses
Double-stranded DNA, nonenveloped viruses
• Simplexvirus (HHV1 and HHV
2)
• Orthopoxvirus
(vaccinia and
smallpox viruses)
• Molluscipoxvirus
• Smallpox,
molluscum
contagiosum,
cowpox
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Double-stranded DNA, nonenveloped viruses
• Hepadnavirus
(Hepatitis B virus)
• Use reverse
transcriptase to
produce DNA from
mRNA
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Single-stranded RNA, + strand, nonenveloped
• Varicellavirus (HHV 3)
• Lymphocryptovirus (HHV 4)
• Cytomegalovirus (HHV 5)
• Roseolovirus (HHV 6)
• HHV 7
• Kaposi's sarcoma (HHV 8)
• Some herpesviruses can
remain latent in host cells
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Single-stranded RNA, + strand, nonenveloped
• Enterovirus
• Enteroviruses
include poliovirus
and coxsackievirus
• Rhinovirus
• Hepatitis A virus
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Single-stranded RNA, + strand, nonenveloped
• Alphavirus
• Hepatitis E virus
• Norovirus (Norwalk
agent) causes
gastroenteritis
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
• Alphaviruses are
transmitted by
arthropods;
include EEE, WEE
• Rubivirus (rubella
virus)
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
9
Single-stranded RNA, + strand, nonenveloped
• Arboviruses can replicate
in arthropods; include
yellow fever, dengue, SLE,
and West Nile viruses
• Hepatitis C virus
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Single-stranded RNA, – strand, one RNA strand
• Vesiculovirus
• Lyssavirus (rabies
virus)
• Cause numerous
animal diseases
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Single-stranded RNA, – strand, one RNA strand
Single-stranded RNA, + strand, nonenveloped
• Coronavirus
• Upper respiratory
infections
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Single-stranded RNA, – strand, one RNA strand
• Filovirus
• Enveloped,
helical viruses
• Ebola and
Marburg viruses
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Single-stranded RNA, – strand, one RNA strand
• Paramyxovirus
• Morbillivirus
• Paramyxovirus
causes
parainfluenza,
mumps and
Newcastle disease
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
• Hepatitis D virus
• Depends on
coinfection with
Hepadnavirus
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
10
Single-stranded RNA, –
strand, multiple RNA strands
Single-stranded RNA, –
strand, multiple RNA strands
• Influenzavirus
(Influenza viruses A
and B)
• Bunyavirus (CE virus)
• Influenza C virus
• Hantavirus
• Envelope spikes
can agglutinate
RBCs
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Single-stranded RNA, –
strand, multiple RNA strands
• Arenavirus
• Helical capsids
contain RNAcontaining
granules
• Lymphocytic
choriomeningitis
• VEE and Lassa
Fever
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Single-stranded RNA, two RNA strands,
produce DNA
• Lentivirus (HIV)
• Oncogenic viruses
• Use reverse
transcriptase to
produce DNA from
viral genome
• Includes all RNA
tumor viruses
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Double-stranded RNA, nonenveloped
• Reovirus (Respiratory
Enteric Orphan)
• Rotavirus
• Mild respiratory
infections and
gastroenteritis
• Colorado tick fever
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
11