Phage Lambda (λ) Flashcards
name 2 physical features on the λ phage
-isocohedral head
-noncontractile tail
what is a bacteriophage?
viruses that infect bacteria
what repressor proteins are key?
-CL protein
-Cro proteins
what classification of bacteriophage is λphage?
ds DNA
name an example of ssRNA
leviviridae
cystoviridae is an example of what class of bacteriophage?
dsRNA
what is a lysogenic phage?
temperate phage
name 2 reproductive options
1-typically
2-lysogeny(remain within the host cell without destroying it)
describe a summary of the prophage stage in lysogeny
phage genome integrates on host bacterial genome- on chromosome for (λ) or plasmids for (P1).most phage genes not expressed. prophage reproduced in synchrony.
what is a lysogen
bacterial host infected w a prophage
what are host cell lysogens immune to?
superinfections by the same virus-phage repressor
decsribe the process of induction
under appropriate conditions, lysogen will lyse & release phage particles
what altered conditions can leave to induction?
host cell damage
what is a cryptic virus?
phage looses ability to leave the host via mutation
where does the integration of phage λ take place?
attachment site in the bacterial & phage genomes (att)
what happens on entry due to complementary base pairing in the lysogenic bacteriophage?
circularisation
att int xis -are all responsible for what stage in organisation of transcripts?
integration & excision
What’s responsible for recombination?
gam red
what does the control region include?
CIII N cI cro CII
O & P are responsible?
DNA replication
what is lysis controlled by?
S
Q is responsible for what stage?
late control
where is early transcription initiated?
P1 & P2
where is termination initated?
tL1 & tR1/tR2
what allows anti-termination & expression of delayed early genes?
The product of gene N & Q(from Pr)
tr3 is the site of what?
rightward transcript termination
what happens if CI wins the race with Cro?
transcription blocked for cro gene, N & Q.lysogeny is established.
what happens if Cro wins the race?
-Cro binds operating sites Or & OL, blocking transcription from the PR & PL
-Represses Pm & CII synthesis. Blocks OI synthesis
-prevents integration of the λ genome into the host chromosome
what triggers induction?
drop in levels of λ repressor(CI) caused by UV exposure
What does Excisionase (Xis)
-binds integrase (int)
-enables integrase to reverse integration process
what happens to the cohesive ends after infection?
theta θ mode-ligated together to form a circular molecule which replicates.
rolling circle mode does what when switched over?
length linear DNA is generated, for further packaging into phage particles
what is rolling circle replication required for?
production of the lytic cycle of replication-which generates multiple length linear DNA
what is the replication forks’ role
proceeds around the template
where is the nick of the primer located?
3’ -OH end
why does temperate phage survive in a bacterium?
due to integration of their DNA into the host chromosome
what can the temperate phage induce?
phenotype changes in the bacterium
Escerichia coli O157:H7 saki strain description?
18 prophage genome,16% of entire genome
what is a MORON?
after more DNA, phage often carries additional genes within elements(after more DNA)
What impacts do MORONs have?
active players in cell physiology —->
become resistant to antibiotics,survive in other enviroments,produce toxins +other virulence factors
where are morons identified?
within the prophage due to different G C content +own promoters & terminators
resistance to quinolones & beta-lactams in E.coli mean what?
altered metabolic capabilities
what allows E.coli to interact with & invade epithelial cells
phage λ protein
what encodes survival of the host immune response-superoxide dimutase
gifsy-2 Salmonella prophage
what protects against free radicals?
superoxide dimutase
what protects E.coli from serum killing?
phage λ Bor protein
exotoxins are involved with what?
bacterial pathogenicity
give examples of defensive countermeasures bacteria use?
surface changes and restriction modifications
helping defend ecological placing because…
phage are important led for acquisition of genes
what does the decreased in fitness of lysogenic hosts mean?
metabolic burden to replicate extra DNA-lysis of the host after prophage induction
what happens when prophage increase the fitness of lysogenic hosts?
immunity(phage repressor) & superinfection exclusion genes of prophage to protect lysogen
give an extended description of the association of Lactobacillus delbruki
lytic phage rare, organism hard to transform with foreign DNA. strong barrier against intrusion of foreign DNA.
what phage is readily detected in milk?
streptococcus thermophilis
other features of streptococcus thermophilis include?
permissive to DNA transfer: few anti-phage mechanisms detected
true or false
proteins secreted from bacteria that are toxic to eukaryotic cells?
true
thick mucopurulent, nasal discharge, fever, sore throat, swollen cervical lymph- are all symptoms of what?
corneybacterium diphtheride
diphtheria is encoded by what?
roxin β-phage
give examples of systemic symptoms of diphtheria
destroys parenchyma of heart, liver, kidneys or adrenal glands
genetic exchange in the enviroment-sewage/water treatments
phage stx 1+2, dtx and sea widespread
what infects cats,cattle,pigs,horses?
transduction of stx between E.coli O157:H7 and commensal s.aureus
what does the transduction of stx between E.coli O157:H7 and commensal s.aureus produce?
enterotoxins SEA.SEB,SEC
what does ampliphi treat?
pseudomonas aureginosa, cystic fibrosis, MRSA, infections of burns
name the different serotypes of cholera
ISS, OI-el Tor, O139:bengal strain
give the line knock on affect of the ingestion of V.cholera
adheres to colonies on small intestine ->
CTX acts on mucosal cells(diarrhoea)
whats encoded on a single gene locus regarding cholera?
incomplete enome of a filamentous bacreiophage CTX
what does the CTX phage lack?
secretin but uses the host secretin encoded by type II secretion apparatus
what integrated filamentous bacteriophage genome carries the cholera toxin gene?
CTX Φ on chromosome 1
what does TCP stand for?
toxin co-regulated pilus
what is TCP a receptor for?
phage CTX Ψ
