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Microbiology Exam 1 (Modules 1&2) > Chapter 5 > Flashcards

Chapter 5 Flashcards

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1
Q

Biological entity that is known to infect every type of cellular organism.

A

Virus

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2
Q

Early researchers found that when infectious fluids were passed through porcelain filters designed to trap bacteria, the fluid that came through was still infectious/pathogenic.

; This result proved that an infection would be caused by a fluid containing agent smaller than bacteria, thus introducing the concept of _________ ______.

A

Filterable virus

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3
Q

This person hypothesized that rabies was caused by a living thing smaller than bacteria

He also proposed the term virus which is Latin for poison

A

Louis Pasteur

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4
Q

Loeffler and Frosch discovered what?

A

An animal virus that caused foot-and-mouth disease in cattle

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5
Q

Ivanovski and Beijerinck showed what?

A

That a disease in Tobacco was caused by a virus.

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6
Q

Seawater contain ___ million viruses per millimeter

A

10 million

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7
Q

What are some questions that remain about virology.

A
  1. Are they organisms; that is, are they alive?
  2. What role did viruses play in the evolution of life?
  3. How can they jump from other species to suddenly cause severe disease in humans?
  4. How can particles so small and simple be capable of causing disease and death?
  5. What is the connection between viruses and cancer? (our entire genome is stored in DNA and accessed in useable pieces in RNA, so if a virus has nucleic acids it can be detrimental to the RNA in our cells.)
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8
Q

Terminology to describe viruses instead of ‘alive’ and ‘dead’

A

Active and inactive

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9
Q

The Viral Debate

A
  1. Since viruses are unable to multiply independently from the host cell, they are not living things and should be called infectious molecules.
    (cannot replicate on their own and require a host cell -> so not alive)
  2. Even though viruses do not exhibit most of the processes of cells, they can direct them, and thus are certainly more than inert and lifeless molecules.
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10
Q

The Vital Role of Viruses in Evolution

A
  • Infect cells and influence their genetic make up.
  • Shape the way cells, tissues, bacteria, plants, and animals have evolved.
  • 8% of the human genome consists of sequences that come from viruses.
  • 10-20% of bacterial DNA contains viral sequences.
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11
Q

What does it mean that viruses are obligate intracellular parasites?

A

It means that they cannot multiply unless they invade a specific host cell and instruct its genetic and metabolic machinery to make and release quantities of new viruses.

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12
Q

Properties of Viruses

A
  • are obligate intracellular parasites of bacteria, algae, fungi, plants, protozoa, and animals
  • The amount of viruses on earth is approximately 10x the amount of bacteria and archaea combined (partially because they multiply so rapidly, and because they can infect so many eukaryotes)
  • Are ubiquitous in nature and have had a major impact on development of biological life
  • Size ranging from 20-1000nm
  • Continued on other slides….
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13
Q

Are not cells; structure is very compact and economical

Do not independently fulfill the characteristics of life

A

Viruses

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14
Q

What is the basic structure of a virus?

A

Consists of a protein shell (capsid) surrounding a nucleic acid core

-> protein coat with a string of nucleic acids

; nucleic acid can be either RNA or DNA but not both
; nucleic acid can be double-stranded DNA or RNA, or single-stranded DNA or RNA

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15
Q

How do viruses multiply?

A

By taking control of the host cell’s genetic material and regulating the synthesis and assembly of new viruses

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16
Q

TRUE or FALSE:

Viruses lack enzymes for most metabolic processes and lack machinery for synthesizing proteins.

A

TRUE

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17
Q

What are the main criteria currently used to group viruses that take into account the actual nature of the virus particles themselves instead of being based on their hosts and the disease they cause?

A

Hosts and diseases they cause, structure, chemical composition, and similarities in genetic make up

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18
Q

International Committee on the Taxonomy of Viruses (ICTV)

A

in charge of classifying and categorizing viruses

*it is difficult to classify viruses, and their classifications are constantly changing

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19
Q

What is a reason that viruses can multiply so rapidly?

A

Because they only have a protein coat and string of nucleic acids to replicate, vs eukaryotes that have multiple structures and organelles to replicate and bacteria/archaea (prokaryotes) that also have more structure to replicate.

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20
Q

Viruses are __________.

A

; ultramicroscopic (has to have a much higher resolution to be visible)
; range from 20-1000nm in size

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21
Q

Viruses are not ___; and their structure is very ________ and ________.

A

; cells
; compact
; economical

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22
Q

TRUE OR FALSE:

Viruses do not independently fulfill the characteristic of life.

A

TRUE

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23
Q

True or False:
Viruses have molecules on their surface that dictate which host cells they should and could attach to.
The molecules also dictate how virulent the virus is.

A

True

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24
Q

According to the ICTV, how many orders and families of viruses are there?

A

8 orders and 38 families

*another 84 families not yet assigned to any order.

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25
Q

5.2 Outcome
Discuss the size of viruses relative to other
microorganisms.

A

smallest infectious agents

more than 2000 bacterial viruses could fit into the average bacterial cell

some range: 0.02micrometers (20 nm) to 150nm

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26
Q

What can the size of a Pandoravirus be compared to?

A

coccus-shaped bacterial cell

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27
Q

Viral architecture is most often observed using _____ stains in combination with electron microscopy.

A

Special

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28
Q

Explain the outer surface of a virus

A

Composed of regular repeating subunits that give rise to their crystalline appearance

-external protein coating

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29
Q

5.3 Outcome

Describe the function and structure(s) of viral capsids

A
  • protein capsid or shell that surrounds the nucleic acid in the central core
  • together capsid and nucleic acid called nucleocapsid
  • each capsid is constructed of identical subunits called capsomeres (which are made from protein molecules)
  • depending on how the capsomeres are shaped and arranged the assembly results in two different types: helical and icosahedral
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30
Q

Many animal viruses also have an additional covering to the capsid called an ______.

A

envelope (usually a modified piece of a host’s cell membrane)

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31
Q

Viruses that consist of only a nucleocapsid (as opposed to also having an envelope) are called _____ _____.

A

naked viruses

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32
Q

A fully formed virus that is able to establish an infection in a host cell is often called a _______.

A

virion

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33
Q

5.2 Outcome

Distinguish between enveloped and naked viruses

A

An enveloped virus has a nucleocapsid and an envelope which likely originated from the host’s cell membrane

A naked virus only has the nucleocapsid

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34
Q

5.2 Outcome

Explain the importance of viral surface proteins, or spikes

A

essential for the attachment of viruses to the next host cell

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35
Q

What viruses are complex capsids found in?

A

only found in viruses that infect bacteria

these viruses are never enveloped

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36
Q

Naked HELICAL nucleocapsids

A

very rigid, tightly wound, cylinder shaped

ie. tobacco mosaic virus

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37
Q

Enveloped HELICAL nucleocapsids

A

more flexible, tend to have a looser arranged helix

ie. influenza, measles, SARS-CoV-2, rabies

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38
Q

Helical capsids

A

rod shaped capsomeres

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39
Q

Icosahedron capsids

A

three dimensional, 20 sided figure with 12 evenly spaced corners; major variations in the number of capsomeres

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40
Q

Naked icosahedron

A

clearly see spikes

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41
Q

Enveloped icosahedron

A

ie. hep B and herpes simplex virus

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42
Q

5.2 Outcome

Describe the possible nucleic acid configurations that viruses may possess.

A

can have either DNA or RNA but not both.

can have single or double stranded RNA or DNA

-RNA genomes may be segmented

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43
Q

DNA Viruses - List examples

A

Variola virus

  • ds
  • causes smallpox

Herpes simplex2

  • ds
  • causes genital herpes

Parvovirus

  • ss
  • causes Erythema infectiosum (skin condition)
44
Q

RNA Viruses - List Examples

A

Poliovirus

  • ss (+) sense
  • causes Poliomyelitis

Influenza

  • ss (-) sense
  • causes flu

Rotavirus

  • ds RNA
  • causes gastroenteritis

HIV

  • ss RNA (carries reverse transcriptase)
  • causes AIDS
45
Q

what type of genome does SARS-CoV-2 have?

A

single stranded (+) sense RNA virus

this means the virus is ready for immediate translation into proteins

46
Q

The structure of a virus contains only those parts needed to invade and control a host:
1.
2.
3.

A

External coating

Core containing one or more nucleic acid strands of DNA or RNA

Sometimes one or two enzymes

47
Q

Viruses lack any _____-______ machinery found in cells.

A

protein-synthesizing

48
Q

The sum total of the genetic information carried by an organism

A

Genome

49
Q

The number of viral genes is quite ____ compared with that of a cell, but the number of viral genes can vary.

A

small

50
Q

The more people that get vaccinated and few people who get infected allows for what

A

viruses have less ability to multiply and mutate into something more virulent

; decreased opportunity

51
Q

Positive-sense RNA:
Negative-sense RNA:
Segmented RNA:
Retroviruses:

A
  1. ready for immediate translation
  2. must be converted before translation occurs
  3. Individual genes exist on separate pieces of RNA
  4. Carry their own enzymes to create DNA out of their RNA (going backwards- think retro clothes/music)

*normally do not create DNA out of RNA

52
Q

Poliovirus and Influenza Virus

A

single stranded RNA

53
Q

Variola and Herpes simplex-s viruses

A

Double stranded DNA

54
Q

Parvovirus

A

Single stranded DNA

55
Q

Rotavirus

A

double stranded RNA

56
Q

HIV

A

single stranded RNA + REVERSE transcriptASE

*ase= enzyme

57
Q

Enzymes for specific operations within their host cell:

Synthesizes DNA and RNA

A

Polymerase

58
Q

Enzymes for specific operations within their host cell:

Replicates a copy of RNA

A

Replicase

59
Q

Enzymes for specific operations within their host cell:

Synthesizes DNA from RNA

A

reverse transcriptase

60
Q

Some viruses carry away substances form their host cells:

Arenaviruses

A

pack along host ribosomes

61
Q

Some viruses carry away substances form their host cells:

Retroviruses

A

borrow the host’s tRNA molecules

62
Q

The way the cycle of a virus seizing control of a host cell works dictates what characteristics?

A
  • the way the virus is transmitted
  • what it does to the host
  • the responses of the immune defenses
  • human measures to control viral infections
63
Q

Step One of 5 Step life cycle of animal viruses

A

Adsorption: a process of adhering one molecule onto the surface of another molecule

64
Q

Step Two of 5 Step life cycle of animal viruses

A

Penetration (viral):

the step in which the virus enters the host cell

65
Q

Step Three of 5 Step life cycle of animal viruses

A

Uncoating:

the process of removal of the viral coat and release of the viral genome by its newly invaded host cell

66
Q

Step FOUR of 6 Step life cycle of animal viruses

A

Synthesis:
viral genetic materials and proteins are made through replication and transcription/translation

  • RNA viruses are replicated and assembled in the cytoplasm
  • DNA viruses enter the host’s nucleus and rep. + assembled there
67
Q

Step FIVE of 6 steps in the life cycle of animal viruses

A

Assembly:

Capsids and and genetic material are packaged into virions

68
Q

Step SIX of 6 steps in the life cycle of animal viruses

A

Release:
the assembled virus particle exits the host cell and moves on to infect another cell

-controlled by size of the virus
-health of the virus
ie. Poxvirus infected cell: 3000-4000 virions
Poliovirus infected cell: 100,000 virions

69
Q

What is the length of time of the replication cycle in multiplication cycles in animal viruses?

A

Varies from 8 hours in polioviruses to 36 hours in herpesviruses

70
Q

Host Range (adsorption)

A

the limitation imposed by characteristics of the host cell on the type of virus that can successfully invade it

ie. Hep B which only infects human liver cells

71
Q

Tropisms

A

specifications of viruses for certain tissues

72
Q

Penetration/uncoating through endocytosis

A

an entire virus is engulfed by the cell and enclosed on a vacuole or vesicle

uncoating by enzymes inside the host cell exposing the nucleic acids

ie. herpesvirus

73
Q

Penetration through direct fusion of the viral envelope with the host cell membrane

A

envelope merges directly with the cell membrane, liberating the nucleocapsid into the cell’s interior

ie. mumps virus

74
Q

Life Cycle of dsDNA viruses

A

early phase:

  • viral DNA enters the nucleus, where genes are transcribed into messenger RNA
  • RNA transcript moves into cytoplasm to be translated into viral proteins required to replicate the viral DNA
  • the host cell’s DNA polymerase is involved in this phase

late phase:

  • parts of the viral genome are transcribed and translated into proteins required to form the capsid and other structures
  • new viral genomes and capsids are assembled
  • mature viruses are released by budding or cell disintegration
75
Q

5.3 Outcome
Define the term cytopathic effect and provide one
example.

A

virus-induced damaged to the cell that changes its microscopic appearance

example: Syncytia
- the fusion of multiple damaged host cells into single large cells containing multiple nuclei

example: poliovirus
- cells are killed completely by shrinking, detaching and lyse

76
Q

5.3 Outcome

Discuss both persistent and transforming infections.

A

Persistent: some cells maintain a carrier relationship and a virus is not immediately lysed:

  • can last from a few weeks to the remainder of a the host’s life
  • can remain latent in the cytoplasm

Transforming: Some animal viruses enter a host cell and permanently alter its genetic material, leading to cancer; these viruses are termed oncogenic.

  • some ways this works are the virus carries genes that directly cause cancer, or the virus produces proteins that induce loss of growth regulation leading to cancer
  • oncoviruses: viruses that can initiate tumors
77
Q

Provirus

A

when viral DNA is incorporated into the DNA of the host
-in relation to persistent infections

  • chronic latent phase: periodically become activated under the influence of various stimuli
    ie. herpes simplex and herpes zoster viruses
78
Q

5.3 Outcome:
Provide thorough descriptions of both lysogenic and lytic
bacteriophage infections.

A

Lysogeny: a condition in which the host chromosome carries bacteriophage DNA without the production of virions

  • Temperament Phages: undergo adsorption and penetration, do not undergo replication or release immediately (less virulent stage)
  • Prophage State: viral DNA inserted into bacterial chromosome, and copied during normal bacterial cell division
  • Induction: process whereby a bacteriophage in the prophage state is activated and begins replication and enters the the lytic cycle
79
Q

Oncoviruses

A

mammalian viruses capable of initiating tumors:

  • Papillomaviruses
  • Herpesviruses
  • Hep B viruses
  • HTLV-I
80
Q

Bacteriophage

A

“bacteria eating” virus

  • this type was discovered in 1915
  • most contain dsDNA
  • often make the bacteria they infect more pathogenic for humans
  • every bacterial species is parasitized by one or more bacteriophages
81
Q

Lysogenic Conversion

A

when a bacterium acquires a new trait from its temperament phage
-Vibrio cholerae - cholera toxin

  • Clostridium botulinum - botulinum toxin
  • occasionally phage genes in the bacterial chromosome cause the production of toxins or enzymes that the bacterium would not otherwise have
82
Q

Adsorption

A

attachment of the virus to its host cell

-has to be attachment and recognition

83
Q

persistent infections

A

long term relationships with viruses

-weeks to for a life time

84
Q

5.4 Outcome:

List the three principal purposes of cultivating viruses

A
  1. Isolate and identify viruses in clinical specimens
  2. Prepare viruses for vaccines
  3. Do detailed research on viral structure, multiplication cycles, genetics, and effects on host cells.
85
Q

5.4 Outcome:

Describe three ways in which viruses are cultivated.

A
86
Q

in vivo

A

method of inoculation of living embryos or animals

87
Q

in vitro

A

using cells or tissues that are cultivated in the lab for study

88
Q

Usual choice of animal cultivation of viruses for study

A

specially bred strains of white mice, rats, hamsters, guinea pigs, rabbits

*insects (invertebrates) or nonhuman primates are occasionally used as well

89
Q

why is a bird egg containing an embryo a common choice for inoculation studies?

A

intact and self supporting life unit

  • sterile environment
  • nourishment
90
Q

types of in vitro cultivation that are a simple and effective way to grow populations of isolated animal cells in culture

A

cell culture or tissue culture

-grown in sterile chambers with special media that contain correct nutrients

91
Q

Monolayer

A

-in relation to in vitro cultivation by cell culture

a single, confluent sheet of cells that supports viral multiplication and allows researchers to closely inspect for signs of infection

92
Q

Plaques

A

in virus propagation methods, the clear zone of lysed cells in tissue culture or chick embryo membrane that corresponds to the area containing viruses

  • virus growth show up as clear well-defined patches in the cell sheet
  • visible manifestation of cytopathic effects (CPEs)
93
Q

Detection of viruses in bacteriophages

A

same technique is used to detect and count bacteriophages as is used in mammalian cells:

  • plaque develops when the viruses released by an infected host cell radiate out to adjacent cells
  • new cells become infected, die, and release more viruses -> process continues
  • plaque manifests as a macroscopic clear spaces that show dead cells
94
Q

5.5 Outcome

Name three noncellular infectious agents besides viruses.

A
  1. Prions
  2. Satellite Viruses
  3. Viroids
95
Q

Prions

A

a cytopathic protein associated with slow-virus spongiform encephalopathies of humans and animals

ie. Mad cow (bovine spongiform encephalopathy)
ie. Creutzfeldt-Jakob disease (CNS gradual degeneration and death)
ie. Shy-Drager Syndrome
- we do not know the exact mode of prion transmission
- composed primarily of protein with no nucleic acid

96
Q

Satellite Viruses

A
  • virus like particles that are dependent on OTHER viruses for replication
    ie. Adeno-associated virus (AAV): initially thought to only replicate in cells infected with adenovirus, but we now know it can infect cells infected with other viruses
    ie. Delta Agent: a naked circle of RNA that is expressed only in the presence of hep b virus -so worsens the severity of sx of hep B
97
Q

Viroids

A
  • in infectious agent, that unlike a virion, lacks a capsid and consists of a closed circular RNA molecule.
  • Although known viroids are all plant pathogens, it is conceivable that animal versions exist
  • about one tenth the size of the average virus
  • significant in plants like tomatoes, potatoes, cucumbers, citrus trees, and chrysanthemums
98
Q

5.6 Outcome
Analyze the relative importance of viruses in human
infection and disease

A
99
Q

5.6 Outcome:
Discuss the primary reason that antiviral drugs are more
difficult to design than antibacterial drugs

A

PRIMARY REASON:
difficult to find drugs that will affect viruses without damaging host cells

-viruses can mutate and become resistant

100
Q

how many viruses are known to infect humans

A

260

101
Q

Common causes of acute infections

A

colds, hepatitis, chickenpox, influenza, herpes, warts

102
Q

Prominent viral infections worldwide

A

dengue fever, Rift Valley fever, yellow fever

103
Q

Infections with high mortality rates

A

COVID-19, AIDS, Ebola

104
Q

Infections that cause long-term disability

A

Polio, neonatal rubella

105
Q

Connection to chronic infections

A

T1DM, MS, various cancers, Alzheimer’s, obesity

106
Q

Almost all antiviral medications are designed to target one of the steps of the viral life cycle

A

; replication

ie. Integrase inhibitor class of HIV drugs interrupts the ability of HIV genetic info to incorporate into the host cell DNA
-&raquo_space;>prevents the integration of DNA

Microbiology Exam 1 (Modules 1&2) (9 decks)

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