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Microbiology > Lesson 3.3 - Viruses > Flashcards

Lesson 3.3 - Viruses Flashcards

(53 cards)

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1
Q

Characteristics of Viruses

A
  • nm (10-9) to um (10-6)
  • obligate intracellular molecular parasites
  • acellular, infectious, diverse
  • DNA or RNA
  • lacks ribosomes & metabolic pathways
  • mutations; responds to natural selection
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2
Q

Viral sizes

A

idkkkk

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3
Q

Viral genomes

A
  • Most are small (5-500 kb)
    • May consist 1+ chromosomes
    • Circular or linear
    • DNA or RNA (some have tRNA)
    • ss or ds
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4
Q

Viral Mutation Rate

A
  • abt. 1 in 10k nts
    • Humans are abt 1 in 1 billion
  • No repair system
  • Frequent reassortment
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5
Q

Viruses in Nature

A
  • Earth’s most abundant biological particles
  • Found in concentrations 10X higher than prokaryotes
  • Don’t always harm host
    • i.e. anelloviruses in blood
    • Nasal secretions, saliva, bile, feces, tears, semen, breastmilk, urine
  • Some benefit host
    • Transduction (bacteriophage)
    • Human genome full of dysfunctional retroviruses
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6
Q

Dimitri Ivanowsky (1892)

A
  • Botanist
  • Causal agent could pass through ceramic filter
  • Flitrate contained poison venom
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7
Q

Martinus Beijerinck (1898)

A
  • Microbiologist; repeated Ivanowsky experiments
  • Virus inactivated by boiling contagious living fluid
    • Tobacco mosaic virus (TMV)
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8
Q
  • Yellow Fever (1902)
  • Rous Sarcoma Virus (1911)
  • Bacteriophages (1915)
  • Fertilized chicken eggs (1931)
A
  • Mosquito vector
  • Oncogenesis
  • -
  • Animal virus cultivation
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9
Q

Crystallization of TMV discovered by [who]

A
  • Stanley (1935)
    • Nobel Prize in Chemistry (1946)
  • Proof that viruses were not cells; made of protein & nucelic acid (DNA or RNA); require a host cell for replication
  • Electron microscope images n/a until 1947
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10
Q

Virus Methods of Infection

A
  • Mucous membranes
    • Rub eyes, inhale droplets
  • GI tract
    • Contaminated food/water, fingers in mouth (ooo)
  • Trauma
    • Animal bite, contaminated needles, mech. injury
  • Genitourinary tract
    • Sexual transmission
  • Plant viruses/seed borne, arthropod vector
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11
Q

How do viruses make us sick?

A
  • Homeostasis disrupted; host cells manipulated to produce viruses
    • Cell lysis, changes in size/shape, nuclear inclusion bodies, cytoplasmic inclusion bodies, mutations, transform to cancer cells, multinucleated cells
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12
Q

Zoonosis

A
  • Animal origin / host / reservoir
  • Naturally transmissible (vertebrae animals to humans)
    • Some b humanized & unaffect animals
      • measles, HIV, Sars-CoV-2
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13
Q

Ebola by [what animals]

A

bats

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14
Q

Rabies by [what animals]

A

mammals

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15
Q

Influenza by [what animals]

A

birds and pigs

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16
Q

SARS by [what animals]

A

civets

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17
Q

Middle East Respiratory Syndrome (MERS) by [what animals]

A

dromedary camels

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18
Q

Sars-CoV-2 by [what animals]

A

bats; suspected pangolins

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19
Q

What does it mean when viruses are polythetic?

A

In a group that cannot be defined on basis of any single shared character, but on overlapping combinations of characters

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20
Q

Type of nucleic acids [Viruses]

A
  • DNA, RNA (some have tRNA), ss, ds
  • Linear, circular
  • (+) strand vs. (-) strand
  • no universal gene
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21
Q

Shape [Viruses]

A
  • Capsid structure; presence/absence
  • Presnce of additional structures
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22
Q

What are some organisms that viruses parasitize?

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A

Bacteria (bacteriophages), Archaea (archaeaphages), insects, mammals, birds, fish, amphibians, plants, amoeba, fungi (mycoviruses), crustaceans

23
Q

Viruses can be classified by taxonomic terms, especially families such as the ____________ suffix

Study These Flashcards
A
  • viridae
  • Governed by International Committee on Taxonomy of Viruses (ICTV)
24
Q

What is the host for Mimivirus?

Study These Flashcards
A

Acanthamoeba polyphaga

Originally thought to be Gram (+)

25
Where do virsues fit in the tree origin of life?
No single evolutionary origin; instead are **vehicles of transfer**
26
Plus (+) strand RNA viruses
Consists mRNA directly translated into proteins
27
Minus (-) strand RNA viruses
Contains viral RNA complementary to viral mRNA
28
Retroviruses
makes a DNA copy of its RNA genome that is inserted into the DNA of the host cell
29
Viron [and terms used to describe it]
* Individual complete virus particle * **Helical** * **Polyhedral** (many sided) * Icosahedral (20) * **Binal** * Pleomorphic (irregular)
30
Define capsid.
* Protein shell enclosing nucleic acid * Built of **capsomeres** * Can be 100s of same or different * **​​​**Nucleocapsid: nucleic acid + capsid
31
Define envelopes.
* Lipid bilayer derived from host cell * Contain viral glycoproteins for infecting cells * i.e. Sars-CoV-2 * [S]pike, [E]nvelope, [M]embrane. [N]ucleocapsid * Without envelope: naked
32
Viral Host Specificity
* Virion binds to host cell membrane receptor * **Lock and Key****​** * noneveloped virus attach via arrangement/ shape of capsids
33
Stages of Virus Replication
* Attachment * Eclipse phase * Penetration and uncoating * Synthesis * Assembly * Release
34
Penetration stage 😏
* Nonenveloped enter by endocytosis * Enveloped enter by endocytosis or fusion * Bacteriophages puncture cell envelope & inject their DNA
35
Uncoating phase
* Host cell removes capsid * Endocytic vesicles low pH * Host cell proteases
36
Eclipse phase
Interval b/t penetration and production of virions
37
Synthesis phase
* Viral DNA escorted to nucleus; replicated * Viral enzymes may be involved * Transcription by host
38
Assembly phase
* Some at plasma membrane * Organelles * RER, Golgi, mitochondria, chloroplasts
39
Release phase
Lysis and budding are most common
40
Cellular Flow of Information [in terms of Viruses]
* Some follow dis, but others bend the rules to their advantage * (+) = sense; message * (-) = antisense; template
41
Baltimore Classification
* Classifies viruses based on genome type * Understand how virus replicated its nucleic acid * Understand how viral mRNA is synthesized
42
DNA Dependent DNA polymerase
Enzyme that catalyzes DNA synthesis from DNA template
43
RNA Dependent DNA polymerase
Enzyme that catalyzes DNA synthesis from RNA template
44
DNA Dependent RNA polymerase
Enzyme that catalyzes RNA synthesis from DNA template
45
RNA Dependent RNA polymerase
Enzyme that catalyzes RNA synthesis from RNA template
46
Class I: dsDNA
* dsDNA -\> mRNA -\> protein * Host DNA-dependent RNA-polymerase * Genome replication: dsDNA -\> dsDNA * Host DNA-dependent DNA-polymerase i.e. Herpes, Smallpox, HPV
47
Class II: ssDNA
* (+) ssDNA -\> dsDNA -\> mRNA -\> protein * Host DNA-dependent DNA polymerase * Host DNA-dependent RNA polymerase * (-) ssDNA -\> dsDNA -\> mRNA -\> protein * Host DNA-dependent DNA polymerase * Host DNA-dependent RNA polymerase i.e. Erythroparvovirus, fifth disease, skin lesions
48
Class III: dsRNA
* (-) RNA -\> mRNA -\> protein * Viral RNA-dependent RNA polymerase (packaged in virion) * makes (+) and (-) strand copies i.e. Rotavirus (diarrhea & vomiting)
49
Class IV: (+) ssRNA
* (+) RNA -\> protein * Codes for RNA-dependent RNA polymerase * synthesize (-) RNA from (+) strand i.e. Norovirus (vomiting & diarrhea), Sars-CoV-2, HepA, HepC
50
Class V: (-) ssRNA
* (-) ssRNA -\> (+) RNA -\> protein * Viral RNA-dependent RNA polymerase (packaged in virion) i.e. Ebola, Measles, Influenza
51
Class VI: (+) ssRNA w/ DNA intermediate
* (+) RNA -\> (+/-) dsDNA -\> mRNA -\> protein * Viral RNA-dependent DNA polymerase; reverse transcriptase * Host DNA-dependent RNA polymerase * Retroviruses i.e. Lentiviruses, HIV
52
Class VII: (+/-) dsDNA w/ RNA intermediate
* Uses reverse transcriptase (P) * Incomplete dsDNA "gapped genome" * Last step: reverse transcriptase activity occurs inside virion * RNA -\> DNA: not shown in image i.e. HepB
53
Baltimore Classification Group I-VII Overview
* I: ds (+/-) DNA viruses * II: ssDNA viruses (majority (+)) * III: ds (+/-) RNA viruses * IV: (+) sense ss (+) RNA viruses * V: (-) sense ss (-) RNA viruses * VI: ss (+) RNA viruses w/ DNA intermediate * VII: ds (+/-) DNA viruses w/ RNA intermediate

Microbiology (17 decks)

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