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microbio km > microbio lecture 10 > Flashcards

microbio lecture 10 Flashcards

1
Q

viruses are genetic information (DNA or RNA) contained within

A

protective protein coat

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2
Q

Inert particles

A

no metabolism, replication, motility

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3
Q

genome hijacks

A

host cell’s replication machinery

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4
Q

inert outside cells

A

inside, direct activities of cell

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5
Q

viruses are

A

Infectious agents, not organisms

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6
Q

viruses require

A

live organisms as hosts; cannot be grown in pure
culture

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7
Q

viruses cannot be seen w/

A

light microscopy

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8
Q

viruses classified generally based on

A

type of cell they infect: eukaryotic
or prokaryotic

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9
Q

Viruses that infect bacteria are called

A

bacteriophages, or phages

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10
Q

Phages easy to grow in the lab as a good model for how animal viruses

A

interact with their hosts

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11
Q

phages are vehicle for

A

horizontal gene transfer

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12
Q

phage ability to kill bacteria
is important

A

ecologically
and medically

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13
Q

virion (viral particle) is

A

nucleic acid surrounded by a capsid

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14
Q

capsid

A

protein coat

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15
Q

capsid composed of simple identical subunits called

A

capsomeres

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16
Q

Capsid plus nucleic acids called

A

nucleocapsid

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17
Q

Nucleic acid is either ___,___

A

DNA or RNA

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18
Q

nucleic acid may be

A

circular or linear, single- or double-stranded

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19
Q

Enveloped viruses

A

surrounded by
lipid bilayer obtained from host cell

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20
Q

enveloped virus have

A

Matrix protein between
nucleocapsid and envelope

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21
Q

Non-enveloped (naked) viruses

A

are more resistant to disinfectants

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22
Q

spikes

A

attach to receptor sites on host cells; phages attach by tail fibers

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23
Q

three shapes of viral architecture

A

icosahedral, helical, complex

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24
Q

icosahedral

A

20 flat triangles

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25
Q

helical

A

Capsomeres arranged in helix

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26
Q

complex

A
  • Phage
  • Icosahedral nucelocapsid (head) and helical protein (tail)
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27
Q

International Committee on Taxonomy of Viruses (ICTV) keeps

A

online database and publishes features, classification, nomenclature of viruses

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28
Q

2015 report

A

> 6,000 viruses → 3,704 species → 609 genera
→ 27 subfamilies → 111 families →7 orders

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29
Q

Viruses: Key characteristics include

A

genome structure (nucleic acid and
strandedness) and hosts infected

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30
Q

in taxonomy, other characteristics like ___ are considered

A

for example, viral shape, disease
symptoms

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31
Q

DNA Viruses: Double Stranded DNA. Papillomaviridae

A

Non-enveloped, look at figure for shape, Human papillomaviruses (some types cause warts; others cause cancers)

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32
Q

DNA Viruses: Double Stranded DNA. Herpesviridae

A

Enveloped, look at figure for shape, Herpes zoster virus (chickenpox); herpes simplex viruses (cold sores, genital
herpes)

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33
Q

RNA Viruses: Doubled Stranded. Reoviridae

A

Non-enveloped, look at figure for shape, Human rotaviruses (diarrheal disease)

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34
Q

RNA Viruses: Single Stranded (plus strand). Picornaviridae

A

Non-enveloped, look at figure for shape, Polioviruses (poliomyelitis); rhinovirus
(colds); hepatitis A virus (hepatitis A)

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35
Q

RNA Viruses: Single Stranded (plus strand). Caliciviridae

A

Non-enveloped, look at figure for shape, Norovirus (gastroenteritis)

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36
Q

RNA Viruses: Single stranded (plus strand), Coronaviridae

A

Enveloped, look at figure for shape, Severe acute respiratory syndrome coronavirus (SARS), Middle East respiratory syndrome coronavirus (MERS)

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37
Q

RNA Viruses: Single stranded (minus strand), Rhabdaviridae

A

Enveloped, look at figure,
Enveloped Rhabdoviridae Rabies virus (rabies)

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38
Q

RNA Viruses: Single stranded (minus strand), Paramyxoviridae

A

Enveloped, look at figure, Mumps virus (mumps); measles virus (measles)

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39
Q

RNA Viruses: Single stranded (minus strand), Orthomyxoviridae

A

Enveloped, look at figure, Influenza virus (influenza)

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40
Q

Reverse transcribing viruses (retroviruses) - DNA, Hepadnoviridae

A

Enveloped, look at figure, Hepatitis B virus (hepatitis B)

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41
Q

Reverse transcribing viruses (retroviruses) - RNA, Retroviridae

A

Enveloped, look at figure, Human immunodeficiency virus (AIDS)

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42
Q

Virus families end in suffix

A

-viridae

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43
Q

Do names follow a consistent pattern?

A

no

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44
Q

some names indicate…

A

appearance (for example, Coronaviridae from
corona, meaning “crown”)

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45
Q

Others named for ____ ___ from which first isolated

A

geographic area (for
example, Bunyaviridae from Bunyamwera in Uganda, Africa)

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46
Q

Genus ends in

A

-virus (for example, Enterovirus)

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47
Q

Species name often name of ______

A

disease
For example, poliovirus causes poliomyelitis
* Viruses commonly referred to only by species name

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48
Q

Viruses often referred to

A

informally

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49
Q

Groups of unrelated viruses sharing….

A

routes of infection

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50
Q

Oral-fecal route:

A

enteric viruses

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51
Q

Respiratory route:

A

respiratory viruses

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52
Q

Zoonotic viruses cause

A

zoonoses (animal to human)

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53
Q

Arboviruses (from arthropod borne) are spread by

A

arthropods; often can infect widely different species

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54
Q

Arboviruses can cause diseases such as

A

yellow fever, dengue fever, West
Nile encephalitis, La Crosse encephalitis

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55
Q

Enteric: mechanism of transmission; common viruses transmitted

A

Fecal-oral route; Enteroviruses (polio), noroviruses, rotaviruses (diarrhea)

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56
Q

Respiratory: mechanism of transmission; common viruses transmitted

A

Respiratory or salivary route; Influenza, measles, rhinoviruses (colds)

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57
Q

Sexually transmitted: mechanism of transmission; common viruses transmitted

A

Sexual contact; Herpes simplex virus type 2 (genital herpes), HIV

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58
Q

Zoonotic: mechanism of transmission; common viruses transmitted

A

Vector (such as arthropods); West Nile encephalitis, Zika virus disease, dengue fever

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59
Q

Zoonotic: mechanism of transmission; common viruses transmitted

A

Animal to human directly; Rabies, cowpox

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60
Q

Three general types of bacteriophages based on
relationship with host

A

Lytic (virulent) phages
Temperate phages
Filamentous phages

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61
Q

General strategies of phage replication

A

Productive Infection; Latent State

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62
Q

Productive infection

A

New viral particles are produced

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63
Q

Latent state

A

Viral genome remains silent within cell, but is replicated along with host cell genome

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64
Q

Lytic or virulent phages exit host by

A

lysing the cell

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65
Q

T4 phage (dsDNA) is model, entire process takes

A

approximately 30 minutes

66
Q

Infection cycle is five step process

A
  • Attachment
  • Genome entry
  • Synthesis
  • Assembly
  • Release
67
Q

Attachment

A
  • Phage attaches to receptors
  • Receptors are molecules that
    typically perform other functions
  • Cells that lack specific receptor
    are resistant to infection by that
    phage
68
Q

Genome entry

A
  • T4 lysozyme degrades cell wall
  • Tail contracts, injects genome
    through cell wall and membrane
  • Capsid remains outside the cell
69
Q

Synthesis of phage proteins and genome

A
  • Early proteins translated within minutes; nuclease degrades host DNA
  • Phage genome synthesized
  • Late proteins are structural proteins
    (capsid, tail); produced toward end of cycle
70
Q

Assembly (maturation)

A

Some components assemble
spontaneously, others require
protein scaffolds

71
Q

Release

A
  • Lysozyme produced late in
    infection; digests cell wall
  • Cell lyses, releases phage
  • Burst size of T4 is approximately
    200
72
Q

Temperate phages can direct a

A

lytic infection or incorporate their DNA into host cell genome
(lysogenic infection)

73
Q

infected cell is

A

lysogen

74
Q

integrated phage DNA is

A

prophage

75
Q

When the cell divides, the prophage

A

is replicated

76
Q

Prophage can begin process of

A

lytic infection

77
Q

Metabolic state of host cell can influence

A

type of infection

78
Q

Lambda phage is

A

model

79
Q

Phage-encoded enzyme integrase inserts phage DNA at

A

specific site on host chromosome

80
Q

Prophage replicates along with

A

host chromosome

81
Q

Phage- encoded enzyme can be excised by phage
encoded enzyme, resulting
in

A

lytic infection

82
Q

A phage encoded repressor prevents

A

excision, maintains lysogenic state

83
Q

Lambda phage

A

DNA excised from chromosome only about
once per 10,000 divisions of lysogen

84
Q

if DNA damaged (for example, UV light exposure), then..

A

SOS repair
system turns on, activates a protease

85
Q

Protease destroys repressor, allows

A

prophage to be
excised, enter lytic cycle

86
Q

phage induction

A

allows phage escape
damaged host

87
Q

Lysogen is immune to

A

superinfection (infection by same
phage)

88
Q

Repressor maintaining integrated prophage also binds to

A

operator on incoming phage DNA, prevents gene expression

89
Q

Lysogen may show change in phenotype due _______ called lysogenic conversion

A

to prophage DNA

90
Q

Toxins encoded by phage genes; only strains carrying ________ produce the toxins

A

prophage

91
Q

Corynebacterium: Medical importance, Property encoded by phage

A

Causes diphtheria; Diptheria toxin

92
Q

Escherichia coli O157:H7: Medical importance, Property encoded by phage

A

Causes hemolytic uremic syndrome; Shiga toxin

93
Q

Streptococcus pyogenes: Medical importance, Property encoded by phage

A

Causes scarlet fever; Streptococcal pyrogenic exotoxins(SPEs)

94
Q

Vibrio cholerae: Medical importance, Property encoded by phage

A

Causes cholera; Cholera toxin

95
Q

Filamentous Phages

A

Single-stranded DNA phages
* Look like long fibers
* Cause productive infections
* Host cells not killed, but grow
more slowly

96
Q

Filamentous Phages continued

A
  • M13 phage is model
  • Attaches to protein on F pilus
    of E. coli
  • Single-stranded DNA
    genome enters cytoplasm
97
Q

In filamentous phages, DNA polymerase of host cells synthesizes complementary strand ->

A

Called replicative form (RF); one
strand used as template for synthesis
of mRNA, copies of genome

98
Q

in filamentous phages, M13 particles assembled
in process of extrusion

A
  • M13 phage coat protein molecules
    inserted into cytoplasmic membrane
  • Other proteins form pores
  • As phage DNA secreted through
    pores, coat proteins coat the DNA,
    form nucleocapsids
99
Q

Generalized Transduction

A
  • Results from packaging error during phage assembly
  • Some phages degrade host chromosome; fragments can
    be mistakenly packaged into phage head
100
Q

These phages cannot direct phage replication cycle

A

Called transducing particles

101
Q

Following release, transducing particles can bind to

A

new host, inject DNA

102
Q

DNA may integrate via homologous recombination, replacing

A

host DNA

103
Q

Any gene from donor cell can be

A

transferred

104
Q

Specialized Transduction

A

Excision mistake during transition from
lysogenic to lytic cycle of temperate
phage
* Short piece of bacterial DNA removed

105
Q

In Specialized transduction, Excised DNA incorporated into

A

phage heads; defective particles released

106
Q

Specialized transudction: bacterial genes may integrate via

A

homologous recombination

107
Q

Specialized transduction: only bacterial genes adjacent to _____ ____ DNA transferred

A

integrated phage

108
Q

Viruses multiply only inside _______

A

living cells

109
Q

must cultivate suitable ____ ____ to grow viruses

A

host cells

110
Q

Plaque assays

A

used to count phage particles in samples:
sewage, seawater, soil

111
Q

Plaque assays: Soft agar inoculated with

A

bacterial host and phage-containing specimen

112
Q

Plaque assays-> after inoculation,

A

Bacterial lawn forms

113
Q

plaques

A

Zones of clearing from bacterial lysis

114
Q

Plaque forming unit (PFU) represents

A

single phage

115
Q

counting plaques yield the titer, which is

A

concentration of
phage in the original sample

116
Q

Animal Virus Replication: Attachment

A
  • Viruses bind to receptors on host cell surface, usually
    glycoproteins on cytoplasmic membrane
  • Often more than one receptor attachment is required (for
    example, HIV binds to two)
  • Normal function of receptor molecule unrelated to viral infection
117
Q

During attachment of animal virus replication, particular viruses must attach to

A

specific receptor; limits cell types and tissues a virus can infect

118
Q

In attachment of animal virus replication, Most viruses infect a

A

single species (dogs do not contract
measles from humans), but that is not always true (rabies
virus infects dogs and humans)

119
Q

Animal Virus replication: Penetration and uncoating

A
  • Enveloped viruses enter by fusion or endocytosis
  • Non-enveloped viruses cannot fuse
  • Entire virion enters cell; nucleic acid separates from protein coat in process of uncoating
120
Q

Animal Virus Replication: Synthesis

A
  • Expression of viral genes to produce viral structural and
    catalytic genes (for example, capsid proteins, enzymes
    required for replication)
  • Often synthesized as polyprotein that is cleaved by viral
    proteases (a target site of antiviral medications)
121
Q

Synthesis of multiple copies of genome

A
  • Three general replication strategies depending on type of genome of virus
122
Q

Three strategies depending on type of genome of virus

A
  • DNA viruses
  • RNA viruses
  • Reverse transcribing viruses
123
Q

Replication of dsDNA viruses

A
  • dsDNA (+/ −) is replicated to form viral genome
  • (−) strand transcribed to produce mRNA; translated to make viral
    proteins
124
Q

Replication of ssDNA viruses

A
  • Complement to ssDNA synthesized first; then acts as template to
    produce more copies of viral genome
  • (−) strand transcribed to produce mRNA
125
Q

Replication of RNA viruses

A
  • Majority are single-stranded; replicate in cytoplasm
  • Require virally encoded RNA-dependent RNA polymerase
    (replicase)
126
Q

Replicase allows use of

A

RNA template to make new strand of RNA

127
Q

Replication strategy varies with viral genome

A

for +, -, or +/-

128
Q

(+) ssRNA genome also serves as

A

mRNA

129
Q

(−)ssRNA genome is complement to

A

mRNA

130
Q

(+/ −) dsRNA genome contains

A

both

131
Q

Replication of (+) ssRNA viruses

A
  • Viral RNA binds to ribosome; produces viral replicase
  • Viral replicase produces multiple copies of complementary (−)
  • RNA strand
132
Q

(+) ssRNA viruses replicated act as

A

templates to produce more (+) strands: Can serve as viral genome or be translated to produce viral proteins

133
Q

Replication of (−) ssRNA viruses

A

Viral RNA and replicase both enter host cell to make complementary (+) RNA strand (REPLICASE MUST ACCOMPANY VIRUS SINCE FIRST STEP IS TO
MAKE (+) STRAND)

134
Q

In (-)ssRNA replication, (+) RNA strand can serve as

A

mRNA to make viral proteins

135
Q

Multiple copies of complementary (−) RNA strand produced to serve as

A

viral genome

136
Q

Replication of dsRNA viruses

A
  • Replicase enters host cell with dsRNA because host cell cannot translate
    dsRNA
  • Replicase uses (−) RNA strand to produce (+) RNA strand
  • (+) RNA strand can serve as mRNA to make viral proteins
137
Q

Replication of RNA viruses

A

Replicase lacks proofreading ability

138
Q

Poor proofreading ability in RNA viruses

A
  • Generates mutations during replication
  • Mutations in surface proteins may not be recognized by immune
    system
139
Q

Antigenic drift

A

antigenic variation because of replicase poor proofreading

140
Q

Some RNA viruses have segmented genomes. When two different viruses or strains infect a host….

A

new viral particles may contain segments from each virus

141
Q

antigenic shift

A

New subtype results from this reassortment of RNA viruses segmented genomes

142
Q

Replication of reverse-transcribing viruses

A
  • Encode reverse transcriptase: makes DNA from RNA
  • Retroviruses have (+) ssRNA genome (such as HIV)
143
Q

Reverse transcriptase enters the

A

cell and synthesizes a single DNA
strand from RNA template

144
Q

As the Complementary DNA strand synthesized,

A

dsDNA integrated into
host cell chromosome

145
Q

Can be transcribed to produce …..

A

new viral genome, mRNA

146
Q

Animal Virus Replication: Assembly and maturation

A
  • Spontaneous self-assembly when viral nucleic acid and capsid proteins accumulate in host cell
  • Site of assembly varies with virus type and affects release
147
Q

Animal Virus Replication: Release

A
  • Most enveloped viruses leave via budding
  • Non-enveloped viruses released when host cell dies, often by apoptosis initiated by virus or host
148
Q

Budding

A
  • Viral protein spikes insert into host cell membrane; matrix
    proteins accumulate; nucleocapsids extruded
  • Covered with matrix protein and lipid envelope
  • Some obtain envelope from organelles
149
Q

The World Health Organization (WHO) named the novel
coronavirus that causes the disease COVID-19….

A

“severe acute respiratory syndrome coronavirus 2” (SARS-CoV-2) in January 2020.

150
Q

The disease is named from a contraction of the term

A

coronavirus disease 2019.

151
Q

This disease was first observed in humans in

A

Wuhan, China in December 2019.

152
Q

The WHO declared COVID-19 a Public Health Emergency of International Concern (PHEIC) on

A

January 30th, 2020

153
Q

Three β-coronaviruses have crossed the species barrier since 2000
SARS-CoV
MERS-COV
SARS-CoV-2

A
  1. SARS-CoV emerged in the Guangdong province of China in 2002 ultimately infecting
    8,098 people and causing 774 deaths across 5 continents
  2. Middle-East respiratory syndrome coronavirus (MERS-CoV) emerged in the Arabian
    peninsula in 2012 and remains a public health concern
  3. SARS-CoV-2 was identified in December 2019
154
Q

Both SARS-CoV and SARS-CoV-2 likely originated from

A

bats as the reservoir,
with small mammals as intermediate hosts between bat and human

155
Q

MERS-CoV originated from

A

a camel reservoir with direct transfer to humans.

156
Q

In addition, four low-pathogenicity coronaviruses are

A

endemic in humans.

157
Q

SARS-CoV-2 characteristics: The S proteins
protrude from the viral surface resembling a

A

crown, or corona

158
Q

SARS-CoV-2 belongs to the genus

A

β-coronavirus, family Coronaviridae

159
Q

SARS-CoV-2 is a _____, with a length of ______

A

enveloped virus with an unsegmented single-stranded positive-sense RNA genome; 30 kb

160
Q

SARS-CoV-2 main structural proteins

A
  • spike (S) glycoproteins
  • envelope (E) glycoproteins
  • membrane (M) glycoproteins
  • nucleocapsid (N) proteins
161
Q

The genome also codes for

A

16 nonstructural proteins that are involved in
viral replication, maturation, and release.

162
Q

Scientists published the genome sequence by

A

January 10, 2020, just one
month after it was first reported; it took over a year to sequence the SARS-
CoV in 2003.

microbio km (6 decks)

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