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Biology 228: Microbiology > Chapter 6 > Flashcards

Chapter 6 Flashcards

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1
Q

What are some traits of viruses?

A
  • Origin: Latin meaning poison
  • Can be seen using electron microscopes
  • Acellular (not consisting of cells)
  • In order to survive and reproduce, viruses must infect a cellular host, making them obligate intracellular parasites.
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2
Q

What are the genetic characteristics of viruses?

A
  • DNA or RNA genome (never both)
  • Genome is surrounded by a protein capsid and, in some cases, a phospholipid membrane studded with viral glycoproteins
  • Lack genes for many products needed for successful reproduction, requiring exploitation of host-cell genomes to reproduce.
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3
Q

What is a host range?

A

Most viruses typically have limited host ranges and infect specific cell types.

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4
Q

What are bacteriophages (or phages)?

A

Viruses that infect bacteria.

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5
Q

What are zoonoses?

A

Viruses that can be transmitted from an animal host to a human host can cause zoonoses.
Virus itself is not zoonoses.

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6
Q

What can viruses do to alter the configuration of cells?

A

Viruses may cause abnormal growth of the host cell or cell death, alter the cell’s genome, or cause little noticeable effect in the cell.

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7
Q

How can viruses be transmitted?

A

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

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8
Q

What are the two different kinds of vectors?

A
  • Mechanical vectors
  • Biological vectors
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9
Q

What are mechanical vectors?

A

Fly picks us pathogen from fecal matter and carries it on its body, fly transfers pathogen to food, person eats contaminated food and then gets sick.

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10
Q

What are biological vectors?

A

Infected mosquito bites uninfected person, infection spreads through body and into red blood cells, second mosquito bites infected person and mosquito may now transmit infection to another person.

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11
Q

How big are viruses?

A

Ultramicroscopic, 20nm to 900nm in length.

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12
Q

What are virions?

A

Virions are acellular and consist of a nucleic acid, DNA or RNA, but not both, surrounded by a protein capsid (composed of protein subunits called capsomeres).
There may also be a phospholipid membrane surrounding the capsid (non-enveloped viruses or enveloped viruses).

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13
Q

What are spikes?

A

Protein structures that extend outward on the virus.

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14
Q

What do spikes do?

A

At the tips of these spikes are structures that allow the virus to attach and enter a cell or enzymes that allow the virus to detach from the cell surface during release of new virions.

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15
Q

What are the three shapes of viruses?

A
  • Helical
  • Polyhedral
  • Complex shapes
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16
Q

Where is the genome located in a bacteriophage?

A

The genome is located within the polyhedral head and the sheath connects the head to the tail fibers and tail pins.

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17
Q

What is classification of viruses based on?

A

Morphology, type of nucleic acid, host range, cell specificity, and enzymes carried within the virion.

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18
Q

How are viruses classified?

A

The ICTV has classified known viruses in seven orders, 96 families, and 350 genera.

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19
Q

What do viral family names end in?

A

-viridae

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20
Q

What do genus names end in?

A

-virus

21
Q

LOOK AT CHART ON CHAPTER 6 SLIDE 14

A
22
Q

What are the 6 stages for viruses to infect host cells?

A
  • Attachment
  • Penetration
  • Uncoating
  • Biosynthesis
  • Maturation
  • Release
23
Q

What are virulent phages?

A

Typically lead to the death of the cell through cell lysis.

24
Q

What are temperate phages?

A

Can become part of a host chromosome and are replicated with the cell genome until such time as they are induced to make newly assembled viruses.

25
Q

What are the two cycles that bacteriophages can have?

A

Lytic or lysogenic cycle.

26
Q

What is the lytic cycle?

A

Leads to the death of the host.

27
Q

What is the lysogenic cycle?

A

Leads to integration of phage into the host genome.

28
Q

VIEW CHAPTER 6 SLIDES 18-20 IMAGES

A
29
Q

What is the growth curve of bacteriophage populations?

A

One-step multiplication curve.

30
Q

What are the four stages of the bacteriophage growth curve?

A
  1. Inoculation
  2. Eclipse
  3. Burst
  4. Burst size
31
Q

What happens in the inoculation stage?

A

Inoculum of virus binds to cells (down).

32
Q

What happens in the eclipse stage?

A

Virions penetrate the cell (flat).

33
Q

What happens in the burst stage?

A

Host cells release many viral particles (up).

34
Q

What happens in the burst size stage?

A

Number of virions released per bacterium (flat).

35
Q

What is transduction?

A

As it assembles and packages DNA into the phage head (biosynthesis and maturation), packaging occasionally makes a mistake. Instead of packaging viral DNA, it takes a random piece of host DNA and inserts it into the capsid (horizontal gene transfer). Once released, this virion will then inject the former host’s DNA into a newly infected host.

36
Q

What are the two kinds of transduction?

A

Generalized transduction and specialized transduction.

37
Q

What is specialized transduction?

A

Both sides of the DNA are going to be that are next to the infection are more likely to transfer to the new bacteria.

38
Q

CHAPTER 6 SLIDE 25 IMAGE

A
39
Q

Animal hosts versus prokaryote hosts.

A

In animals, virus fully enters the cell via endocytosis or membrane fusion.
Latency versus lysogeny.

40
Q

What is latency?

A

Undergone in animals. Similar to lysogeny for a bacteriophage.

41
Q

What is tissue tropism?

A

Most viruses only infect certain types of cells within tissues.

42
Q

What are the four different genome types in viruses?

A

dsDNA, ssDNA, dsRNA, ssRNA (can be + or -)

43
Q

Retroviruses (SLIDE 29)

A

HIV puts its DNA into cell of interest.

44
Q

What are the types of persistent infections?

A
  • Latent infection
  • Chronic infection
45
Q

What is a latent infection?

A

Has periods of acting up, will go away for a while and can return without having to be reinfected.

46
Q

What is a chronic infection?

A
47
Q

6.3 Summary

A
  • Viral cultivation requires the presence of some form of host cell (whole organism, embryo, or cell culture).
  • Viruses can be isolated from samples by filtration.
  • Viral filtrate is a rich source of released virions.
  • Bacteriophages are detected by presence of clear plaques on bacterial lawn.
  • Animal and plant viruses are detected by cytopathic effects, molecular techniques (PCR, RT-PCR), enzyme immunoassays, and serological assays (hemagglutination assay, hemagglutination inhibition assay).
48
Q

6.4 Summary

A

Other acellular agents such as viroids, virusoids, and prions also cause diseases. Viroids consist of small, naked ssRNAs that cause diseases in plants. Virusoids are ssRNAs that require other helper viruses to establish an infection. Prions are proteinaceous infectious particles that cause transmissible spongiform encephalopathies.
* Prions are extremely resistant to chemicals, heat, and radiation.
* There are no treatments for prion infection.

Biology 228: Microbiology (20 decks)

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