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Baker Semester One > Acellular Pathogens > Flashcards

Acellular Pathogens Flashcards

1
Q

Who postulated that rabies was caused by a virus?

A

Louis Pasteur

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2
Q

What did Ivanovski and Beijerinck find?

A

That a disease in tobacco was caused by a virus

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3
Q

Viruses

A

noncellular particles with a definite size, shape, and chemical composition

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4
Q

Characteristics of Viruses

A

-Infectious, acellular pathogens
-Obligate intracellular parasites with host and cell-type specificity
-DNA or RNA genome (never both)
-Genome surrounded by a protein capsid

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5
Q

Host range

A

The range of host species and cell types a virus can infect

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6
Q

Phages/bacteriophages

A

Viruses that infect bacteria

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7
Q

Vector

A

An animal that transmits a pathogen from one host to another

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8
Q

Viruses can be transmitted through…

A

direct contact, indirect contact with fomites, or through a vector

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9
Q

Mechanical vectors

A

When the arthropod carries a viral pathogen on the outside of its body and transmits it to a new host by physical contact

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10
Q

Biological vectors

A

When the arthropod carries the viral pathogen inside its body and transmits it to a new host through biting

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11
Q

Capsids

A

-Protein coat that encloses and protects the nucleic acid of the virus
-Made up of capsomers
-All viruses have them

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12
Q

Capsomers

A

Identical protein subunits which make up facets of the capsid

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13
Q

Viral Envelope

A

-An external covering around the virus (including around the capsid)
-Most animal viruses
-Acquired when the virus leaves the host cell
-Spikes (exposed proteins on the outside of the envelope) help with attach of the virus to the host cell

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14
Q

Naked virus

A

Lacks an envelope

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15
Q

Helical virus

A

Continuous helix of capsomers forming a cylindrical nucleocapsid

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16
Q

Polyhedral or Icosahedral capsid

A

A three dimensional, 20-sided structure with 12 ventricles

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17
Q

What are the functions of the Capsid/Envelope?

A

-Protects the nucleic acid when the virus is outside the host cell
-Helps the virus bind to a cell surface and assists the penetration of the viral DNA or RNA into a suitable host cell

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18
Q

Why are poxviruses complex/atypical?

A

They lack a typical capsid and are covered by a dense layer of lipoproteins

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19
Q

Viral genome

A

-Either DNA or RNA but never both
-The number of genes varies for each type of virus
-Carries genes necessary to invade host cell and redirect cell’s activity to make new viruses

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20
Q

What are the main criteria presently used to classify viruses?

A

-Viral genetics
-Chemistry
-Morphology
-Mechanism of multiplication

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21
Q

Family name of a virus ends in

A

-viridae

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22
Q

Genus name of a virus ends in

A

-virus

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23
Q

DNA viruses

A

-Usually double-stranded but may be single-stranded
-Circular or linear

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24
Q

RNA viruses

A

-Usually single-stranded
-May be double-stranded
-May be segmented into separate RNA pieces
-Positive sense or negative sense

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25
Positive-sense RNA
ssRNA genomes ready for immediate translation
26
Negative-sense RNA
ssRNA genomes that must be converted into proper form (positive sense RNA)
27
Cornavirus (Family of Coronaviridea)
-Enveloped and have non-segmented, ssRNA+ (single-stranded, positive sense RNA)
28
General Lytic Cycle of a Virulent phage
1. attachment 2. penetration 3. biosynthesis 4. maturation 5. lysis
29
Attachment portion of lytic cycle
The phage attaches to the surface of the host
30
Penetration portion of lytic cycle
The viral DNA enters the host cell
31
Biosynthesis portion of lytic cycle
phage DNA replicates and phage proteins are made
32
Maturation portion of lytic cycle
New phage particles are assembled
33
Lysis portion of lytic cycle
The cell lyses, releasing newly made phages
34
Temperate/Lysogenic Phage
The phage integrates its genome into the host bacterium's chromosome as a prophage-- Does not lyse the cell immediately
35
Prophage
A bacteriophage genome that's integrated into a bacterial cell's chromosome or exists as plasmid
36
Lysogeny
A viral reproduction cycle where a phage's DNA integrates into a host bacterium's genome and the viral DNA is retained and copied during the bacterial cells normal cell division, resulting in a transfer of the temperate phage genome to all host cell progeny
37
Lysogenic cycle of a virulent phage
1. Attachment 2. Penetration 3. Phage DNA becomes incorporated into host genome 4. Cell divides and prophage DNA is passed onto daughter cells 5. Under stressful conditions the prophage DNA is excised from the bacterial chromosome and enters the lytic cycle 1. Biosynthesis 2. Maturation 3. Lysis
38
Induction
the process by which a temperate phage switches from the lysogenic state to the lytic pathway
39
Hepatits B Host range
Human liver cells
40
Poliovirus host range
primate intestinal and nerve cells
41
Rabies host range
various cells of many mammals
42
Endocytosis of a virus
Entire virus is engulfed and enclosed in a vacuole or vesicle
43
Fusion of a virus to a cell membrane
Envelope merges directly with membrane resulting in nucleocapsids entry into cytoplasm
44
Viral uncoating
the breakdown or removal of the capsid causing the release of the viral genome into the cell
45
Where are DNA viruses generally replicated?
In the nucleus
46
Where are RNA viruses generally replicated and assembled?
in the cytoplasm
47
Budding (exocytosis)
Nucleocapsid binds to membrane which pinches off and sheds the viruses gradually; cell not immediately destroyed
48
Lysis
Nonenveloped and complex viruses released when cell dies and ruptures
49
Cytopathic effects (virus-induced damage to cells)
-Changes in size and shape -Cytoplasmic inclusion bodies -Inclusion bodies -Cells fuse to form multinucleated cells -Cell lysis -Alter DNA -transform cells into cancerous cells
50
Persistent infections
cell harbors the virus and is not immediately lysed
51
Chronic latent virus
a virus that remains in the body for a long time without causing symptoms but can reactivate later to cause repeat infection
52
Examples of persistent infections with a chronic latent state
-Measles virus -Herpes simplex virus -Herpes zoster virus
53
Herpes simplex virus
cold sores and genital herpes
54
Herpes zoster virus
chickenpox and shingles
55
Oncoviruses
mammalian viruses capable of initiating tumors
56
Papillomavirus
An oncovirus responsible for cervical cancer
57
Epstein-Barr virus
An oncovirus responsible for Burkitt's lymphoma
58
Steps in Transduction
1. Viral attachment and penetration 2. Integration 3. Excision 4. Infection 5. Recombination
59
Integration step in transduction
the phage DNA becomes incorporated into the host genome
60
Excision step in transduction
The phage is excised from the bacterial chromosome along with a short piece of bacterial DNA. The DNA is then packaged into newly formed capsids
61
Infection step in transduction
Phage containing both viral and bacterial DNA infect a new host cell
62
Recombination step in transduction
The phage DNA, along with the attached bacterial DNA, are incorporated into the new cell
63
Differences in Bacteriophage and Animal Virus Multiplication
-In bacteriophage, there is the precise attachment of special tail fibers to cell wall whereas in animal virus there is attachment of the capsid or cell envelope to cell surface receptors -In bacteriophage there is no uncoating of the nucelic acid, it is injected through the cell wall. In animal viruses the whole virus is engulfed and uncoated or viruse fuses with cell memrbane
64
Techniques in Cultivating and Identifying Animal Viruses
-Cell cultures -Bird embryos -Live animal inoculation
65
Prions
-misfolded proteins, contain no nucleic acid -Extremely resistant to usual sterilization techniques -Cause transmissible spongiform encephalopathies (fatal neurodegenerative diseases)
66
Prion diseases common in animals
-Scrapie (goats and sheep) -Bovine spongiform encephalopathies (mad cow disease) -Wasting disease (elk) -Creutzfeldt-Jakob Syndrome (humans)
67
Satellite viruses
Dependent on other viruses for replication
68
Adeno-associated virus
A satellite virus that replicates only in cells infected with adenovirus
69
Delta agent
A satellite virus with a naked strand of RNA expressed only in the presence of hepatits B virus
70
Viroids
short pieces of RNA, no protein coat; only identified in plants
71
Latent infection vs Chronic infection
Latent remains hidden and dormant in cell during a phase called latency Chronic is consistent or recurrent over a long time

Baker Semester One (6 decks)

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