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BM211 microbiology > Block D 3 > Flashcards

Block D 3 Flashcards

viruses of archaea and bacteria

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Biology 101 flashcards
1
Q

virus

A

genetic element that cannot replicate independently of a living (host)

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2
Q

virology

A

study of viruses

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3
Q

virus particle (virion)

A

extracellular form of a virus

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4
Q

what does a virion contain

A

nucleic acid genome surrounded by a protein coat (capsid) and in some cases other layers of material

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5
Q

4 phases of the viral replication attachment (adsorption) of the virus to host cell

A

-entry (penetration) of virion or nucleic acid
-synthesis of virus nucleic acid and protein
-assembly of capsids and packing of viral genomes
-release of mature virions from host

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6
Q

what type of curve is virus replication typically characterised by

A

one step growth curve

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7
Q

what is the latent period of virus life cycle

A

eclipse and maturation

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8
Q

what is burst size of virus life cycle

A

number of virions released

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9
Q

how is quantification of bacterial virus carried out

A

plaque assay

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10
Q

what do the best studied bacteriophages infect

A

enteric bacteria

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11
Q

what do most phages contain

A

dsDNA genomes

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12
Q

most bacteriophages are naked but what do some possess

A

lipid envelopes

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13
Q

what do most viruses that infect archaea resemble

A

those that infect enteric bacteria

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14
Q

how many infections are initiated per second

A

10^25

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15
Q

10^14 g phages on earth is approx. the same total mass of what

A

homo sapiens (50kg per person)

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16
Q

attachment of virion to host cell is said to be what

A

highly specific

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17
Q

attachment and entry of bacteriophage T4 requires complementary receptors on what

A

the surface of susceptible host and its infecting virus

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18
Q

what do receptors on host cell carry out for cell

A

normal functions (eg uptake proteins, cell to cell interactions)

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19
Q

what do the receptors include (in attachment and entry of bacteriophage T4)

A

proteins
carbohydrates
glycoproteins
lipids
lipoproteins
complexes

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20
Q

what does the attachment of a virus to its host cell result in

A

changes to both virus and cell surface that facilitate penetration

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21
Q

what is a permissive cell

A

host cell that allows the complete replication cycle of a virus to occur

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22
Q

what is bacteriophage T4

A

virus of E.coli
one of the most complex penetration mechanisms

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23
Q

in the attachment of bacteriophage T4 virions attach to cells via what

A

tail fibres

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24
Q

what do the tail fibres that attach virions to cells interact with

A

polysaccharides on E.coli cell envelope

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25
Q

in attachment of bacteriophage T4 the tail fibres then contract, what does the tail coremake contact with

A

E.coli cell wall

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26
Q

what do the lysozyme like enzyme form in attachment and entry of bacterio. T4

A

small pore in peptidoglycan

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27
Q

once the tail sheath has contracted what happens with the viral DNA in attachment and entry of bacterio. T4

A

viral DNA passes into the cytoplasm

28
Q

what type of genome does T4 have

A

dsDNA

29
Q

T4 a genome that is said to be what

A

circularly permuted and terminally redundant

30
Q

what is restriction modification system and what is it only effective against

A

DNA destruction system
only against double stranded DNA viruses

31
Q

example of restriction enzyme

A

restriction endonuclease

32
Q

what do restriction enzymes do

A

cleave DNA at specific sequences

33
Q

what does modification of hosts own DNA at restriction enzyme recognition sites prevent

A

cleavage of own DNA

34
Q

what are the 3 viral mechanisms to evade bacterial restriction systems

A

-chem modif. of viral DNA (glycosylation or methylation)
-production of proteins that inhibit host cell restriction system
-T4 containing a modified base

35
Q

what is the name of the modified base that T4 has that helps evade bacterial restriction systems

A

5-hydroxymethylcytosine
its DNA is resistant to virtually all known restriction enzymes

36
Q

what are the 3 parts that the T4 genome can be divided into

A

early
middle
late proteins

37
Q

what stages are the enzymes needed for DNA rep and transcription (replication of bacteriophage T4)

A

early and middle proteins

38
Q

what are late proteins

A

head and tail proteins and enzymes req to liberate mature phage particles

39
Q

what stage of proteins are needed for
the synthesis and glucosylation of hydromethylcytosine

A

early proteins

40
Q

what stage of proteins are needed for
enzymes that function of T4 replisome

A

early proteins

41
Q

what stage of proteins are needed for
proteins that modify host RNA pol

A

early proteins

42
Q

what stage of proteins are needed for
additional proteins that modify host RNA pol

A

middle proteins

43
Q

what stage of proteins are needed for
production of viral proteins

A

middle proteins

44
Q

what stage of proteins are
synthesised later

A

late proteins

45
Q

what stage of proteins
include proteins of virus coat

A

late proteins

46
Q

what stage of proteins are
synthesised in larger amounts

A

late proteins

47
Q

in the packaging of the T4 genome double stranded DNA is pumped into head under pressure using what

A

ATP

48
Q

in packaging of T4 genome after head is filled with DNA what other components are added

A

T4 tail
tail fibres
+ more

49
Q

virulent mode

A

viruses lyse host cells after infection

50
Q

temperate mode

A

viruses replicate their genomes in tandem with host genome and without killing host

51
Q

temperate viruses

A

can undergo a stable genetic relationship within the host
(but can also kill cells through lytic cycle)

52
Q

lysogeny

A

state where most virus genes are not expressed and virus genome (prophage) is replicated in synrony with host chr.

53
Q

lysogen

A

a bacterium containing a prophage

54
Q

what is the genome of bacteriophage lambda

A

linear
dsDNA

55
Q

what is bacteriophage lambda

A

complementary
single stranded
12 nucleotides long at the 5’ terminus of each strand

56
Q

what forms upon penetration of bacterio. lambda

A

the cos site

57
Q

what occurs once cos site has been formed

A

DNA ligates and forms double stranded circle

58
Q

when lambda is lysogenic what happens to its DNA

A

integrates into E.coli chr at lamba attachment site
(attλ)

59
Q

what occurs when bac. λ enters lytic pathway

A

λ synthesises long linear concatemers of DNA by rolling circle replication

60
Q

what is the regulation of lytic vs lysogenic events in λ controlled by

A

complex genetic switch
2 repressor proteins

61
Q

what repressor proteins causes repression of λ lytic events
(activates lysogeny)

A

cl protein
(the λ repressor)

62
Q

what repressor protein controls activation of lytic events
(represses lysogenic genes)

A

cro repressor

63
Q

what is the key to the balance of the 2 repressor protein in the cell

A

the physiology of the bacterial host

64
Q

what drives bacterial evolution

A

transfer of DNA from one cell to another by a bacteriophage due to mispacking of the bacteriophage genome

65
Q

what are the names of the 2 modes of transduction

A

generalised transduction
specialised transduction

66
Q

generalised transduction

A

DNA from any portion of the host genome is packaged inside the virion

BM211 microbiology (14 decks)

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