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BIOL 4010 Virology > Section 4 > Flashcards

Section 4 Flashcards

1
Q

Giant viruses are called:

A

Nucelocytoplasmic large DNA viruses (NCLDVs)

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1
Q

NCLDVs facts

A
  • 6 families
  • large ds DNA geomes
  • share sets of “core” genes
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2
Q

NCLDVs #1:

A

Phycodnaviruses

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3
Q

Phycodnaviruses

A

viruses that infect algea (best studied eukaryotic viruses)

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4
Q

Phycodnaviruses (PBCV-1) infect:

A

Chlorella alga symbionts that live in paramecium

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5
Q

Phycodnaviruses (PBCV-1) stands for

A

paramecium bursary chlorella virus

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6
Q

PBCV-1 structure:

A

icosahedral with
1- spike at one vertex that attaches to cell
2- fibers sticking out from capsid that also help with its attachment
3- rigid cell wall

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7
Q

Inside PBCV-1 virion at the vertex where the spike is looks different because

A

it has lower density than rest of the virion due to more packaged protein and less DNA

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8
Q

PBCV-1 attaches to virus at spike and makes a _____ through the algae cell wall then proteins are released into the cells cytoplasm

A

hole

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9
Q

Phycodnaviruses have been found in ______ and show decline in performance on cognitive tests

A

brain

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10
Q

Mice that were infected with virus containing algae showed: (3 things)

A

1- decline in cognitive test performance
2- 1/3 had antibodies against the virus
3- showed changes in genes associated with cognitive function and immunity

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11
Q

algae that have chalk plates on the outside of their cells: __________

viruses that infect this chalk type of algae: _____________

A

coccolithophores

cocolithoviruses

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12
Q

coccolithophores form:

A

large blooms in ocean seen from space due to their chalky exterior
when blooms end, lots of cocolithoviruses are found in seawater

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13
Q

cocolithoviruses (ex. EhV-86) encode

A

proteins that synthesize the sphingolipid ceramide

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14
Q

sphingolipid ceramide from cocolithoviruses are involved in: (2 things)

A

1- forming lipid rafts in cells membrane to allow virus to exit
2- blocking the cells apoptosis pathway to allow the virus to keep replicating

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15
Q

effect of cocolithovirsues on climate

A

1- Lysis of these algeal cells releases volatile chemical DMS (dimethyl sulfide) that forms clouds
2- these clouds prevent sunlight to ocean and block phytoplankton growth
NEGATIVE FEEDBACK

3- white cliffs or Dovers made from liths come out

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16
Q

A small eukaryote (picoeuaryote) that is comparable in size to a girus

A

ostreococcus

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17
Q

ostreococcus can can get infected by virus leading only ________ viruses to be produced inside the cell due to space limitations

A

5-15

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18
Q

NCLDVs #2:

A

mimiviruses

mimi= mimicking microbe

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19
Q

mimiviruses infect:

A

amoeba cells

20
Q

Mimivirus genome facts: (5 things)

A

1- linear dsDNA
2- has 900 nt inverted repeats at the ends (speculated to circulate during infection)
3- bigger than some bacterial genomes
4- found many genes that have never been found in a viral genome and are considered cellular genes
5- contain many translation genes but not enough to encode protein synthesis by itself

21
Q

How did the genome of mimivirus get so big?

A

there are repeated gene and partial genome duplications (38% of the genome is from duplication events)

mostly at ends

22
Q

Minivirus genome contains: (5 fun facts)

A

1- contains many genes not found in other viruses and considered cellular
2- contains genes recently acquired from cellular sources
3- contains many Orphan genes
4- contains many genes with evolutionary connections to other genes
5- contains many duplicated genes

23
Q

Why is mimivirus so good at transmission?

A

having a large genome and a large virus structure allows amoeba to mistake it for bacterium and ingest it (taken into a phagosome) leading to infection

24
Q

mimivirus strucrure

A
  • star shaped at one vertex “stargate”
  • multiple membrane layers
  • long protein/sugar fibers that make it resemble bacteria
25
Q

Under the stargate shaped there is ____ _________ and intead, it is filled with proteins that are involved in the first stages of infection

A

no DNA

26
Q

once star-shaped vertex opens:

A

viral membrane and phagosome membrane fuse and DNA is released into cytoplasm

27
Q

mimivirus replication and assembly happens in ______ _______ in the host cells cytoplasm and NOT in the nucleus like usual

A

viral factory

28
Q

viruses released from edges of _____ _______

A

viral factory

29
Q

how are viruses made in viral factories

A

DNA packaged into particles at the outside edge of the factory and it exits through a portal on the opposite end of the stargate opening

30
Q

speculated that mimiviruses can cause ___________

A

pnemonia

31
Q

people that get infected by viruses after being exposed to infected amoebae that act as _____ ________ to bring giruses into humans

A

trojan horses

32
Q

even bigger viruses related to mimiviruses have been found called _______ and ________

A

mamavirus and megavirus

33
Q

megavirus has ____% of its genome NOT similar to mimivirus

A

25

(same genes are in center and different genes are at end)

34
Q

why are same genes are in center and different genes are at end

A

ends of genomes are hotspots for evolution while middle is more conserved and stable

35
Q

Virophage (virus of a virus) Example:

A

Sputnik

36
Q

sputnik replicates within an amoebae that is also infected with __________ as it replicates in its factory

A

mamavirus

37
Q

Sputnik sometimes ends up in mamvirus particles and it can disrupt mamavirus replication and lead it to produce _______ ______

A

defective particles

38
Q

Another girus ______ _____ ______ (____) infects marine protists that eats bacteria

A

cafeteria roenbergensis virus (CroV)

39
Q

CroV infects a marine protist host that is analogous to amoeba but is a diff eukaryote and it can ALSO get infected by a virophage called ______

A

Mavirus

40
Q

Mavirus exists as a _____ _______ in the eukartoyic microbe for defence

A

integrated element

provides defence to the cell against corresponding virus and are now found in eukaryotic genomes

41
Q

Pandoraviruses ALSO infects ______ and is TWICE the size of mimivirus

A

amoebae

42
Q

Pandoravirus VS mimivirus

A
  • Both infect amoeba
  • Both have membrane fusion function for opening the particle to release the DNA & virion contents into the cytoplasm similar to mimivirus stargate
  • Both have the virus maturing in the infected cell starting at the apex going backwards to package DNA

BUT pandora x 2 the size

43
Q

Pithovirus VS pandoravirus

A
  • pithovirus even larger virion (but not that big of a genome!)
    -pithovirus isolated from permafrost
  • both have structure on one end that mediates fusion with cells membrane to release contents into cytoplasm
  • pithovirus has lattice structure when viewed straight on
44
Q

Where did giruses come from?

A

1- bacterium infected by tectivirus was a endosymbiont that became mitochondria
2- tectivirus became a “polinton” (type of transposon) that was encoded in the nucleus
3- polinton escaped the nucleus and gained some cellular genes
4- the escaped version swapped genes and became the progenitor of mega viruses
5- polintons evolved more and became virophages adenoviruses bidnaviruses etc

45
Q

many of girus genomes contain different _____ _____ ______ within them

A

mobile genetic elements (MGE)

46
Q

proposed that MEGs are symbionts within the viral genome as they assist the virus in _____-______ ______ when there is many viruses trying to infect the same cell

A

virus-virus competition

(MEG makes virus win, virus wins, and MEG gets more distributed SYMBIOSIS)

47
Q

Two types of MGE

A

1- restriction/modificatiom systems: degrade other viral DNA and host DNA and use it for their viruses replication
2-Homing endonuclease introns: splice out from genome and into the competing virus inactivating its genes/proteins

BIOL 4010 Virology (20 decks)

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