Deck 9: Viruses of Archaea

Question 1

The filaments attached to one end of the Sulfolobus spindle-shaped virus 1 are thought to be involved in which of the following processes?

A) Degradation of the host cell wall
B) Attachment to the surface of host cells
C) Injection of the genome into the host cell
D) Movement of the virus particle through the environment
E) Maintaining the structure of the virion

Answer 1

B

Question 2

Viruses that infect archaeal cells have been observed to have all of the following virion shapes EXCEPT:

A) Bottle shaped with a wide and a narrow end
B) Spherical
C) Brick shaped
D) Filamentous
E) Lemon-shaped

Answer 2

C

Question 3

Which of the following is a description of an IS element?

A) A short transposable DNA sequence
B) A region of DNA where transcription begins
C) A telomeric-like sequence at the ends of the DNA
D) A region of the host chromosome where the viral DNA integrates
E) A region of DNA that acts as an origin or replication

Answer 3

A

Question 4

Archaea cells contain a nucleus like eukaryotic cells.

Question 5

Even though many of the viruses that infect archaeal cells do not kill their host, they often do which of the following?

A) Shut down host protein synthesis
B) Increase the cell doubling time
C) Decrease the cell doubling time
D) Shut down genome replication
E) Inhibit synthesis of host cell membranes

Question 6

Archaea are singled-celled microorganisms that share which of the following characteristics with eukaryotic cells?

A) Initiate translation of proteins with a methionine, not N-formyl-methionine.
B) Contain histone-like proteins to condense their genomic DNA.
C) Use a TATA-binding protein to initiate transcription of their genes.
D) Have similar enzymes involved in DNA replication .
E) All of the above are correct.

Question 7

What is unusual about the virion of the Acidianus two-tailed virus?

A) The virion contains two tails, one at each end of a lemon-shaped virion.
B) The two tails can be of different lengths.
C) The only requirement for tail production is temperatures above 75ᵒC.
D) The tails are elongated after the virion leaves the host cell.
E) All of the above are correct.

Question 8

Some of the viruses that infect archaeal cells have linear dsDNA genomes with covalently closed ends.What is a major advantage of this feature?

A) It makes the genome more stable under low pH conditions.
B) It allows the genome to be more easily packaged into the virion
C) It allows the genome to be more easily integrated into the host cell genome.
D) It allows the genome to use a self-priming mechanism for DNA replication.
E) All of the above are correct.

Question 9

The extrusion of the tails on the Acidianus two-tailed virus requires which of the following?

A) Temperatures above 75ᵒC
B) An exogenous source of energy
C) Cofactors from the host cell
D) Cofactors from the virus
E) High salt concentration

Question 10

What information was used to identify the three domains of life?

A) Sequence of the 16S ribosomal RNA
B) Sequence of the mitochondrial genome
C) Sequence of the cytochrome c gene
D) Chemical structure of the cell wall
E) Chemical structure of phospholipids

Question 11

What is the function of the large pyramidal structures that are produced during infection with the archaeal virus SIRV-2, which is a member of the Rudivirus family?

A) They are sites of viral gene expression.
B) They lyse the host cell and release virions from the cell.
C) They are part of the virion assembly complex.
D) They are structures involved in viral DNA replication
E) They are involved in inhibiting host cell functions.

Question 12

Most archaea viruses resemble bacteriophages with an icosahedral head and a helical tail.

Question 13

Into which of the following genes in the host cell genome does the archaea virus SSV-1 integrate its genome?

A) DNA polymerase
B) RNA polymerase
C) Transfer RNA
D) Translation initiation factor
E) Ribosomal RNA

Question 14

Viruses that infect archaeal cells have been isolated from all of the following environments EXCEPT:

A) Hot springs with temperatures over 80ᵒC
B) Environments with a pH of 0
C) Solfataric fields that emit sulfur gases
D) The surface of the moon
E) Environments with salt concentrations over 1.5M

Question 15

Even though the two archaeal viruses HHPV-1 and HRPV-1 are clearly related to each other, based on genome and virion structures, they have one major difference.Which of the following describes this difference?

A) One can undergo lysogeny while the other can only carry out lytic infection.
B) One infects hyperthermophilic hosts while the other infects a hyperhalophilic host.
C) One packages a dsDNA genome while the other packages a ssDNA genome.
D) One appears to encode an obvious DNA polymerase while the other does not.
E) One has a linear genome while the other has a circular genome.

Question 16

Which of the following terms specifically describes archaeal organisms that can grow above 80ᵒC?

A) Thermophile
B) Hyperhalophile
C) Hyperthermophile
D) Methanogen
E) Extremophile

Question 17

Which of the following characteristics is common to many of the viruses that infect archaeal cells and distinguishes them from the phages that infect bacteria.

A) They release mature virions without lysing the host cell.
B) Their viral genomes are very high in AT basepairs.
C) Their viral genomes are linear.
D) Their viral genomes are composed of double-stranded RNA.
E) Their virions are composed of icosahedral capsids.

Question 18

Which of the following can be found at the ends of the genome of a virus that infects archaeal cells?

A) Covalently bound protein
B) Inverted terminal repeats
C) Telomeric-like repeat sequences
D) Covalently closed ends
E) All of the above can be found.

Question 19

Which of the following techniques can be used to induced an integrated copy of the archaea virus SSV-1 to begin expressing viral genes?

A) Exposure of cells to low pH
B) Exposure of cells to high salt concentrations
C) Superinfection with the same strain of virus
D) Growth of cells at lower temperatures
E) Exposure of cells to UV light

Question 20

The archaea virus SSV-1, which infects a host organism that lives at 80ᵒC, has a positively supercoiled genome.What is the advantage of this?

A) It reduces local unwinding of the DNA.
B) It makes it easier for DNA to be unwound during replication.
C) It makes it easier for DNA to be unwound during transcription.
D) It prevents tangling of the genomic DNA.
E) It allows histone proteins to condense the genome.

Question 21

Infection of the archaeal cell Acidianus with the virus ATV at the suboptimal temperature of 75ᵒC leads to a productive lytic infection rather than lysogeny.

Question 22

Rudiviruses, a family of archaea viruses, are different from most other archaea viruses in that they lyse the host cell to release mature virions.

Question 23

Some of the viruses that infect host cells in the euryarchaeota phyla have similar virion structures as the head-tail viruses in the Myoviridae and Siphoviridae families.

Question 24

Many of the viruses that infect archaeal cells primarily carry out a lysogenic infection.Even if they do enter a productive infectious cycle, they can release new virions without killing the host cell.What might be the evolutionary advantages of these lifestyle features?

Question 25

In comparing the genomes of the viruses that infect archaeal cells, very few of the viral genomes have genes encoding an identifiable DNA polymerase.Give two possibilities that explain this observation.