bacteriaphage Flashcards
exam 4
viruses that infect bacteria
bacteriophages
simple bacteriophage
capsid + DNA or RNA
some viruses have a lipid coat
envelope
phages adsorb to specific receptors on the
bacterial cell surface
binding of bacteriophage to outer membrane is
irreversible
1 bacteriophage is made up of
multiple phage proteins
early mRNA is synthesized from
1-12 after infection
late mRNAs are synthesized from
8-35 after infection
phage T7 Genome early mRNA has what type of terminator
both factor dependent or independent
E. coli “Host” RNA polymerase recognizes the ___________ and transcribes the early mRNA but it does not recognize the _____________
E. coli “Host” RNA polymerase recognizes the Early promoter and transcribes the early mRNA but it does not recognize the Late promoters
T7 gene 1 encodes
GP1
a phage encoded RNA polymerase specific for the late T7 late promoters
GP1
prevents all subsequent host RNA transcription as well as phage T7 early RNA trnscription
action of Gp2
T7 gene 2 product
GP2
binds to host RNA polymerase holoenzyme and totally inhibits transcription initiation activity
GP2
virulent phages always undergo the ____ growth program
lytic phages
can undergo lytic and lysogenic growth programs
Temperate phages i
is a Temperate phage
bacteriophage lambda
transcriptional Anti-terminator (2)
N and Q
early anti terminator
N
late anti-terminator
Q
represor of lytic growth
Cl
repression of lytic growth
lysogeny
CII is a
binding protein
once CII has had time to accumulate it will activate
cI
site specific
integration
lambda integration is between
gal and bio
cI shuts off
PL and PR
once cI binds to the PR a second promoter forms called
PRM
positive transcriptional of its own synthesis
cI
typically, the only protein expressed from a prophage is the
repressor
immune to any other lambda phage infection
lambda lysogen
lytic growth or lysogeny?
depends on the nutriotional status of the cell
rich nutrient medium> high levels of protease > cII is degraded > No repressor made> Q protein accumulates
Lysis
all of cII is degraded and no repressor is made
lysis
poor nutrient medium > low levels of protease > cII accumulates and activates cI repressor synthesis
lysogeny
enoguh cII is spared to activate transcription resulting in high levels of cI repression
lysogeny
can prophages escape from the lysogenic state?
Yes
escaping the lysogenic state
induction
phage induction is elicited by _____ through the __________
phage induction is elicited by DNA damage through the SOS response
are not expressed in general beucase they are repressed by the LexA protein
SOS- DNA repair
After interaction with activated _______ protein, the Lex A represor ____, allowing the SIS DNA repair genes to be expressed
After interaction with activated Rec A protein, the Lex A represor self-destruct, allowing the SIS DNA repair genes to be expressed
How does the SIS response affect a prophage?
DNA damage activates RecA protein leading to activated RecA protein triggers phage repressors to self-destruct
Similar to the Lex A repressor, phage repressor are triggered undergo _____________ after interaction with activated host RecA protein
autoproteolysis
loss of phage repressor leads to initiation of prophage from the _______ and subsequent lytic growth
bacterial chromosome
host chromosomes regions on either side of the prophage integration site can be mistakenly excised and packaged in a phage particle and subsequently delivered to a new bacterium
misexcision
who can do specialized transduction
only temperate phages
transfer of host bacterial chromosomal DNA limited to the ________ regions of a prophage integration site was ________ and packaged in phage particles and delivered to another bacterium
transfer of host bacterial chromosomal DNA limited to the flanking regions of a prophage integration site was misexcised and packaged in phage particles and delivered to another bacterium
transfers phage genes and specific bacterial genes adjacent to the prophage
specialized transduction
is the acquisition of a new property (phenotype) by a host bacterium due to establishment of lysogeny by a temperate phage
lysogenic conversion
shiga-like toxin
E.coli and lambda phage
phage resistance mechanisms [3]
- alter phage receptor
- restriction modification systems
- crispr systems
each spacer matches a
phage DNA sequence
Guide RNA with an endonuclease will
cleave if there is a match between the strands
