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Principles of Microbiology > Viruses > Flashcards

Viruses Flashcards

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1
Q

What is used to screen for the nucleic acids in phages?

A

Genome Mining - to know scale.

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2
Q

Is there more eukaryotic or prokaryotic cells in nature?

A

There is many more prokaryotic.

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3
Q

How much do viruses amount to in terms of biomass %?

A

5%

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4
Q

What is a basic virus structure?

A

Protein coat, specific strand of RNA, DNA om each one - designed for specific targets/hosts.

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5
Q

Why are viruses called obligate anaerobes?

A
  • no metabolism on their own
  • cannot replicated outside of another living cell
  • depend on other cells for resources
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6
Q

Where does macromolecular synthesis of the virus’ component part take place?

A

Making of nucleic acid and protein, for some viruses a lipid bilayer membrane as a cloak around the outsid eof the particle.

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7
Q

What is one virus particle called?

A

Virion

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8
Q

What is the basic function of a virion?

A

To deliver viral genome into a host cell where it can be replicated.

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9
Q

How do virions move outside of living cells?

A

Via the laws of thermodynamics - can move one stable structure at one energ ylevel but can change, for virus once they come into contact with a cell.

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10
Q

What happens when a virion comes into contact with a living cell?

A

Connections with outer glycoproteins - biochemistry of the living cell makes changes to the virion lowering its energy level then the virion starts the process of delivering the genome of the virus to the living cell.

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11
Q

What is an example of a virus with a lipid bilayer?

A

The herpes simplex viruses (1 and 2)

SARS - CoV 2

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12
Q

What is an example of a naked virus?

A

Reovirus - causes gastrointestinal infections and diarrhoea and is a major cause of infant mortality in developing countries.

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13
Q

What is approx a virus diameter, how can it be viewed?

A

25 - 300nm, electron microscope.

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14
Q

What is the family of viruses and members of the family that can be seen using a powerful light microscope?

A

Mimiviridae - poxviruses (smallpox) an example is mimivirus itself has a big diameter of 750nm, with more than 900 open reading framed in the genome making them able to encode a lot of information.

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15
Q

What is the name of the classification system for organising viruses?

A

The Baltimore classification.

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16
Q

How does the baltimore classification sort out viruses?

A 
dsDNA
ssDNA
dsRNA
\+ssRNA
-ssRNA 
ssRNA -RT
dsDNA-RT
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17
Q

What is a +ssRNA?

A

This is where there is a single stranded RNA, positive sets can be read by ribosomes.

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18
Q

What is -ssRNA?

A

This is where there is a single stranded RNA, negative sets - have to carry in polymerase protein as they have to be transcribed for allowing gene expression and replication.

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19
Q

What is an example of a dsRNA?

A

reovirus (also naked)

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20
Q

What may a virus need to bring to help with replication and gene expression?

A

Its own virus polymerase.

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21
Q

What is the central dogma of living cells?

A
  • in living cells, the genetic blueprint is encoded in double stranded DNA molecules.
    Through the process of transcription, catalysed by RNA polymerase enzymes, coding information with the genomic DNA transformed into molecules of mRNA.
    Ribosomes then ‘read’ and ‘translate’ the information related to them by mRNA into the protein product.
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22
Q

What does dsDNA-RT mean and give an example?

A

This is double stranded DNA which uses reverse transcription for gene expression and replication. Example: Hep B

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23
Q

What are the 3 hypotheses as to the origins of viruses?

A

(1) Progressive (escape) hypothesis:
- viruses arose from genetic elements, parts of genomes that gained the ability to move between cells.
(2) Regressive (reduction) hypothesis: states that viruses are remnants of cellular organisms.
(3) Virus first hypothesis:
states that viruses predate or co-evolved with their current hosts.

24
Q

What is the Sars CoV-2 diameter?

A

100nm

25
Q

What is the purpose of the virus parcel?

A

Wrapped to protect the nucleic acid genome in the ‘outside-world’

26
Q

What is the dictation of which mechanisms of entry into the cell are possible?

A

Lipid envelope?

The composition of the virion dicatates.

27
Q

Who discovered the first virus and when? Which virus?

A

Ruska and Knoll - first electron microscope = 1931

First Tobacco Mosaic Virus

28
Q

What are the 3 components that all virus particles contain?

A
  1. Genome can be DNA or RNA (virions never contain both)
  2. Capsid (compromises structural proteins and in some viruses replicative enzymes.
  3. Attachment (spike) proteins - target the virus to specific host cells. These are proteins on the surface of the virion which have cell surface molecules.
29
Q

What distinguishes viroids from prions?

A

The presence of both protein and nucleic acids.

30
Q

What are prions?

A

These are small infectious agents that contain only RNA and only protein respectively.

31
Q

What do most large viruses, larger than 60nm contain?

A

Envelopes & glycoproteins.

Most are composed of a lipid bilayer - obtained as a new virus buds off through a membrane of the infected cell.

32
Q

What is the role of the glycoprotein?

A

Involved in the attachment of the virus to the receptor on the susceptible cell.

33
Q

What are envelope viruses more susceptible to, what is its function?

A

They are more fragile to environmental destruction - susceptible to detergents or inorganic solvents such as alcohol or soap.
They are less stable to the environment - cloaking function to hide the more antigenic particles from the host immune system

34
Q

What do naked viruses have on their outside?

A

Capsids

35
Q

What is an example of an enveloped virus?

A

Influenza virus

36
Q

What is the role of neuraminidase?

A

Aids in the penetration of the mucus layer of airways - helps viruses get away from cells after infection has taken place (replication), new virus particles budding away from cell.

37
Q

What is the role of Haemagglutinin?

A

Aids in cell attachment and virulence, aids in the process of fusion.
Ex: 11 segments in the flu virus genome all have to assembled to make a new virus.

38
Q

What is the nucleocapsid?

A

This is the term to describe the full assembly of the genome and capsid protein that lies at the core of the virus particles.

39
Q

What are the two types of nucleocapsid symmetry?

A

Helical, Icosahedral

40
Q

What is an example of the helical structure of the nucleocapsid and what are some of its characterisitics?

A

Tobacco Mosaic

  • Structural subunits : capsomeres
  • 1 protomer/3 bp RNA
41
Q

What is an example of Icosahedral structure of the nucleocapsid and what are some of its characteristics?

A

20 triangles
25-200nm
28nm = poliovirus (picornavirus)
smallpox

42
Q

What is an adenovirus?

A

This is made up of 252 capsomeres - each cap made with hexons.

  • 12 are pentavalent fibers
  • 70-90nm
43
Q

Who was the first person to image a coronavirus virion?

A

Almeida from nasal washings. 1960

44
Q

What are 4 components of the coronavirus particle?

A
  • spike protein
  • RNA and N protein
    Envelope
    Hemagglutinin esterase dimer (HE)
45
Q

What do some coronavirus particles have at their surface, associated with the lipid envelope?

A

Hemagglutinin esterase dimer

46
Q

What type of coronavirus is SARs CoV -2?

A

A norvel beta coronavirus

47
Q

What are the components of the Sars CoV-2 virus?

A
  • positive sense RNA
  • encodes for 29 protein (4 are structural)
  • Spike forms a trimeric spike protein
  • membrane
  • nucleocapsid
  • envelope
48
Q

How many kilbases are in the +ssRNA of sars cov2?

A

29 kilobases, encoding for 29 proteins

49
Q

How is the 600kDA trimeric spike protein of Sars CoV 2 held in place?

A

To attraction to lipid bilayer and lipid transmembrane protein.

50
Q

What is a unique characteristic to severe acute resp syndrome coronavirus 2 when isolated in cell culture ?

A

Shows numerous spherical particles that are in the cisternae of the RER/golgi complex of the cell.
Black dots are visible in the cross sections through the viral nucleic acid through the nucleocapsid.

51
Q

What two types of particles are evident in the Sars-CoV2 ?

A

Both ellipsoidal and spherical enveloped particles.

52
Q

What is the coronavirus RNP packaging arrangements and Virion shape?

A
  • Beads on a string stoichiochemistry through interactions between virus genomic RNA, nucleocapsid protein and M protein.
  • More tetrahedral - more likely to the overall virion was ellipsoidal (oval)
  • More hexagonal RNP arrangements promote more circular virions.
53
Q

What is the coronavirus enigma composed of?

A

It is wrapped into a ribonucleotide particle, by multiple copies of the virus encoded N protein.
This approx 30kb long RNP must be packaged into the 80nm diameter lumen of the virus particle.

54
Q

What is the approx diameter of the single stranded RNPs of the corona virus?

A

15-18nm.

55
Q

How is it possible to see the spike proteins at the surface of the Sars CoV 2 virion?

A
  • images made possible by computed tomography, build 3D images from multiple cross sections obtained from X-ray crystallography.
56
Q

How does the Sars CoV 2 gain entry to the cell?

A

It has a cell receptor that binds to the virion spike protein which is called ACE 2. The cellular protease TMPRSS aids in the entry process.

57
Q

How is the spike protein attached to the virion?

A

At the surface of the virus particle, using virus attachment and fusion protein.

Principles of Microbiology (7 decks)

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