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Virology > 4 Bacteriophage 2 > Flashcards

4 Bacteriophage 2 Flashcards

1
Q

What is Tectiviridae

A

PRD1

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2
Q

What is the structure of PRD1

A

Linear ds DNA with protein (P8) bound to each end

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3
Q

What capsid does PRD1 have

A

Icosahedral

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4
Q

What are the membranes of PRD1 like

A

Internal membrane within capsid

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5
Q

What binds to host in PRD1

A

Any spike can act as a receptor to bind to host

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6
Q

what does PRD1 host range/receptor infect

A

Any gram-negative cell that contains the broad host-range plasmid - RP4

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7
Q

Where does PRD1 bind

A

Phage does not bind to pills instead binds to DNA transfer apparatus

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8
Q

How is DNA transfer mediated by the membrane

A

Outer membrane penetration requires proteins
Membrane containing P11 forms tube
Delivers enzyme to make hole in PG (P7)
Fusion with cell membrane results in DNA transfer

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9
Q

What occurs in PRD1 infection

A

Receptor recognition (P2) irreversible binding
Outer membrane penetration (P11)
PG digestion (P7) deliver P7 enzyme through outer membrane - fusion of lipids in tube and mechanisms
DNA translocation

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10
Q

How are PRD1 core subunits

A

Translation in cytoplasm
Before release from ribosome start to form core trimers
First part of protein spontaneously forms trainers
When released from ribosome have unstructured tails - wait till virus made high enough concentration
As they pack, form coiled interface structures - line up form hexon structures

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11
Q

PRD1 replication cycle

A
  1. Proteins self assemble, form capsid subunits
  2. Structural membrane proteins located in cell membrane of host
  3. Vision assembly at host membrane
  4. Host membrane with vision proteins engulfed during formation of capsid shells
  5. DNA packaged by P9 ATPase
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12
Q

How does phage MS2 replicate

A

Positive strand RNA enters cell
1. Directly translated to make early phage proteins for DNA replication
2. Also used to synthesise negative strand RNA from positive stand template
Translated to make more vital structural proteins
Positive strand packaged into capsid shells
Lysis protein translated from positive strand

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13
Q

What is negative strand RNA used for

A

Used as template to make more copies of positive strand

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14
Q

What is an example of dsRNA phage

A

Cystoviridae

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15
Q

What is cystoviridae in eukaryotes

A

Reovirus

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16
Q

What can be seen through a microscope when looking at a cystoviridae

A

Lipid

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17
Q

What is cystoviridae related to

A

Closely related to reoviridae

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18
Q

What is reoviridae

A

Rotavirus that infects humans

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19
Q

What does cystoviridae infect

A

Infects plant pathogenic bacterium Pseudomonas syringe
Binds to host cell via type IV pilus
Retractable ‘twitching’ pili

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20
Q

What is the structure of cystoviridae

A

Genome with 3 dsRNA genome fragments
Packaged into pro capsid core
Procapsid covered by protein shell

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21
Q

What is on the procapsid shell of cystoviridae

A

Lipid containing molecule

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22
Q

How does cystoviridae infect

A
  1. Bind to type IV pilus
  2. Fusion of P6/P3 with outer membrane
  3. Cell wall degraded
  4. Filled procapsid crosses inner membrane
  5. Filled procapsid RNA polymerase copies genome, RNA polymerase reading inside and makes molecules on outside
  6. mRNA makes new procapsid proteins
  7. Replication stops when new P8 protein shell made around filled procapsid
  8. Membrane proteins inserted into inner membrane form phage envelope
23
Q

How are cystoviridae packaged

A

Part of procapsid has specific binding site for small RNA molecule
Nucleus acid guided into procapsid shell - negative charge of nucleic acid repel proteins so they reorganise and form a new shape
Specific binding site on shell form - directed into shell
Form fully structured shell with a segment of each

24
Q

Phage P1

A

Myoviridae

25
Q

What are the myoviridae ends like

A

Ends of linear genome are identical

26
Q

What is terminal redundancy

A

Copies of terminal genes in each molecule

27
Q

What are the ways myoviridae can be joined

A

RCR linear phases joined st ends 1-10 (concatamers)
Sticky ends cut precisely
Or
Package more than one genome worth 1-10 and 1-2 of next

28
Q

What is the Phage P1: lysogenic phage

A

Pro-phage is plasmid
It’s not integrated into host chromosome (just stays inside cytoplasm as a plasmid)
1 or 2 copies of plasmid exist per cell, which are copied at cell division
Phage encodes special stability functions to ensure (one copy goes to each cell) plasmid not lost from cell so virus persists

29
Q

Phage P1 - transduction induction to lyric phase

A

P1 nuclease digests host cell genome (nucleases cuts DNA)
- bacterial DNA is cut at random places
Pieces of bacterial genome about same sizes as P1 can be accidentally packaged into viral particle

30
Q

What do phage particles act as in transduction

A

Phage particles now act as a way of transferring bacterial genes between cells

31
Q

What does phage transfer lead to

A

New combinations of genes in bacteria

32
Q

How can a mutation in lysogenic cycle be repaired

A

Movement to another host cell of same type can repair mutations in genes due to homologous recombination

33
Q

What is phage P1 variable host range

A

P1 changes its host range by an invertible DNA region
If fragment switches orientations with promoter at start can express different segments
Switching process can occur randomly in cell
Different cells express different orientation and broadens diversity of where DNA can go

34
Q

What is the Myoviridae phage like

A

Temperate lysogenic phage

35
Q

What is the shape of the myoviridae phage

A

dsDNA phage with 37 kbp genome
Icosahedral head
Helical tail
6 tail fibres

36
Q

Phage Mu genome map - C

A

C gene controls lysis/lysogeny

37
Q

Phage Mu genome map - A

A

A gene required for transposition event

38
Q

Phage Mu genome map - att site

A

Att site is not a specific sequence, att site defined at end by transposase binding site

39
Q

Phage Mu genome map - G region

A

Invertible responsible for host range - can switch host range

40
Q

What happens to phage Mu after infection

A

Random insertions of Mu prophage make mutations of host chromosome

41
Q

What was phage Mu used for

A

Early tool for insertional mutagenesis E.coli

42
Q

Why is it called Mu

A

Phage mutator

43
Q

How many insertions occur in lysogenic state of phage Mu

A

One

44
Q

What controls the phage Mu insertion

A

C gene

45
Q

What is the phage Mu life cycle

A

Linear DNA enters cell via phage particle
Mu DNA inserted into recipient genome via non-replicative ‘cut and paste’ mechanism
- causes duplication of 5 np of host DNA
transposition mediated by A protein

46
Q

What are he possible effects of Mu lysogeny on host cell

A
  1. Deletion by recombination between two Mu genomes or transposons in same orientation
  2. Inversion by recombination between two Mu genomes or transposons in opposite orientations
47
Q

How does a deletion by recombination occur

A

Pairing of Mu genomes or transposons
Crossover
Homologous recombination makes deletion
Deleted segment and chromosome each contain one Mu genome or transposon

48
Q

How does an inversion recognition occur

A

Pairing of Mu’s or transposons in opposites orientations
Pairing of Mu’s or transposons
Crossover
Homologous recombination makes inversion
Reversed inverted segment

49
Q

Wild type Mu in phage Mu life cycle

A

Wild type Mu lysogeny are stable and not induced by UV or other DNA amazing agents

50
Q

What happens when C is inactivated in phage Mu life cycle

A

A and B proteins are expressed

51
Q

When is Ts mutant inactivated

A

Ts mutant C inactivated at 42degrees

C falls apart

52
Q

Why does the cells in Mu life cycle mutate

A

Cell dies due to number of mutations

53
Q

What are the late gene products made in Mu life cycle

A

Includes phage capsids, tails, lysis proteins

Virology (15 decks)

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