Bacteriophage

Question 1

what is a bacteriophage

Answer 1

viruses that infect bacteria

Question 2

what does a phage particle generally consist of

Answer 2

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

Question 3

what is a virus

Answer 3

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

Question 4

why does the replication of phage require host cell machinery

Answer 4

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

Question 5

what is the lytic phage replication cycle

Answer 5

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

Question 6

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

Answer 6

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

Question 7

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

Answer 7

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

Question 8

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

Answer 8

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

Question 9

what drives the translocation of the DNA into the host cell

Answer 9

the pressure within the capsid

Question 10

what are the early genes expressed in phage reproduction

Answer 10

DNAse and DNA replication machinery

Question 11

what does the early DNAse do

Answer 11

degrades the host genomic DNA which opens up important nucleotides

Question 12

when is the DNA replication machinery produced

Answer 12

when the DNA is circularized

Question 13

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

Answer 13

capsid proteins, DNA packaging machine, holins and lysins

Question 14

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

Answer 14

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

Question 15

how do bacterial cells detect the phage DNA from their own

Answer 15

they methylate their DNA so nucleases know what to selectively degrade

Question 16

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

Answer 16

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

Question 17

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

Answer 17

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

Question 18

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

Answer 18

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

Question 19

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

Answer 19

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)

Question 20

what is transduction / how does it happen

Answer 20

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

Question 21

what are the two type of transduction

Answer 21

Generalized transduction and Specialized transduction

Question 22

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

Answer 22

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

Question 23

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

Answer 23

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

Question 24

what is specialized transduction / which cells can do it

Answer 24

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

Question 25

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

Answer 25

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

Question 26

what is the major driver of bacterial and eukaryotic evolution

Answer 26

bacteriophage evolution

Question 27

what is the analogous system in both bacteria and eukarya

Answer 27

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)

Question 28

can bacteriophage be used to fight infection in eukarya

Answer 28

yes