Bacteriophage Flashcards

1
Q

what is a bacteriophage

A

viruses that infect bacteria

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2
Q

what does a phage particle generally consist of

A

a genome (ssDNA or dsDNA) contained within a protein capsid

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3
Q

what is a virus

A

a noncellular particle that infects a host cell and directs it to produce progeny particles

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4
Q

why does the replication of phage require host cell machinery

A

energy production and nutrient aquisition, particle building blocks (nucleotides and amino acids), protein synthesis

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5
Q

what is the lytic phage replication cycle

A
  1. bacteriophage attaches to host cell 2. phage inserts its DNA (genome) 3. phage genome circularizes 4. cell synthesizes capsid proteins 5. host DNA is degraded and cell replicates phage genome 6. phage DNA is packaged into capsids 7. host cell is lysed to release phage progeny
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6
Q

how do bacteriophage perform step one of the lytic cycle (attach to the bacterium) / is this attachment specific / how does specificity possibly differ

A

the tail fibers on the phage have tips that contain proteins that bind to important bacterial surface molecules / yes this attachment is specific / could be species specific or strain within a species specific

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7
Q

what is a capsular polysaccharide / how do phage get around it

A

it defends the cell against phage infection as a physical barrier / they have enzymes on the tip of their tail fiber that chews through the polysaccharide and binds to the LPS

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8
Q

how does the viral DNA enter the bacterium / what does the tail fiber do for insertion of DNA

A

when the phage attaches it triggers a structural rearrangement of phage tail sheath (contracts) / it penetrates the host cell envelope that releases the phage genome

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9
Q

what drives the translocation of the DNA into the host cell

A

the pressure within the capsid

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10
Q

what are the early genes expressed in phage reproduction

A

DNAse and DNA replication machinery

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11
Q

what does the early DNAse do

A

degrades the host genomic DNA which opens up important nucleotides

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12
Q

when is the DNA replication machinery produced

A

when the DNA is circularized

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13
Q

what are the late genes produced in replication and particle assembly of phage

A

capsid proteins, DNA packaging machine, holins and lysins

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14
Q

what do the capsid proteins do / what does the DNA packaging machine do

A

they self-assemble to form empty particles / loads the phage particle with replicated genome (uses ATP)

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15
Q

how do bacterial cells detect the phage DNA from their own

A

they methylate their DNA so nucleases know what to selectively degrade

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16
Q

what do holins do for cell lysis / what do lysins do for cell lysis

A

they create a hole in the membrane of the cell / they chew up peptidoglycan which explodes the cell

17
Q

what is the difference between a lytic phage and a temperate phage

A

temperate phages integrate themselves into the host genome once the phage DNA is injected

18
Q

how do temperate phages integrate their DNA into a host / what happens to the phage once integrated

A

the integrase recognizes a specific attachment site on the host chromosome and integrates into that specific locus / it goes dormant

19
Q

what is the integrated phage called / when does a temperate phage come out of its bacterial cell

A

a prophage / it stays in the host genome and is vertically transmitted to the progeny until environmental signals trigger the lytic cell conversion (reenters the lytic phage replication)

20
Q

what is transduction / how does it happen

A

the process in which bacteriophages carry host DNA from one cell to another / occurs accidentally as a result of the phage life cycle

21
Q

what are the two type of transduction

A

Generalized transduction and Specialized transduction

22
Q

what is generalized transduction /which phages can do this / how does it happen

A

when part of the undegraded host DNA gets packaged into the capsid / both lytic and temperate phages can do this / host DNA does not fully degrade

23
Q

what is a phage containing host DNA called / are these particles specific to what DNA they can hold / can a transducing particle cause infection

A

a transducing particle / no it can be any piece of the host DNA / no they cannot but they can cause a change in the genotype of the recipient cell

24
Q

what is specialized transduction / which cells can do it

A

when a temperate phage re-enters the lytic cycle and does not re-circularize correctly taking some host chromosome with it / only lysogenic temperate phages because it requires lytic reactivation

25
Q

what is the result of infection of a new host with a specialized transducing particle / what can this lead to

A

gene transfer from the previous host to the new host / can lead to infection or can cause change in the genotype of the recipient

26
Q

what is the major driver of bacterial and eukaryotic evolution

A

bacteriophage evolution

27
Q

what is the analogous system in both bacteria and eukarya

A

the STING protein that turns on antiviral within cells does the same thing in bacteria but causes the degradation of all NAD (kills the cell)

28
Q

can bacteriophage be used to fight infection in eukarya

A

yes