Vibrio cholerae Flashcards
What 5 barriers must cholera cross to cause disease?
1) ingestion
2) gastric acid barrier
3) colonize upper small intestine
4) produce/excrete toxin
5) disseminate in watery diarrhea
What 2 components make up the cholera toxin?
1) CtxA
2) CtxB
CTX B forms protein coat around A
A is cleaved into A1 and A2
Cholera toxin binds host _____ receptor to get into the cell
GM1
A1 subunit enters cell
Once inside the cell, what does A1 do?
modify a G protein to activate adenylyl cyclase
What happen to cAMP levels when cholera infects?
INCREASE
What virulence factor is involved in colonization?
single polar flagellum (nonmotile strains are less virulent)
What happens to the flagellar genes once the bacteria has colonized?
turned off, toxin genes turned on
What virulence factors are involved once bacteria has colonized?
1) TCP (toxin colonization pilus)
2) ACF (accessory colonization factors)
Activation of the ______ regulon permits synthesis of virulence factors
ToxR
True or false: ToxR and ToxS form a regulon
True
What determines whether or not the ToxRS operon is on? (aka what turns the promoter on?)
low temp (outside host)
toxR and S are synthesized and incorporated into cytoplasmic membrane
Where do ToxR and S go once translated?
into the cytoplasmic membrane
What does the R and S stand for?
R = regulator S = environmental sensor
What happens in the stomach once vibrio is swallowed?
high temps inactivated toxRS but the already made proteins still sit in the membrane
When and where does the ToxRS regulon turn on?
in host intestine once ToxS has received a signal unique to the intestinal environment
Once ToxS gets the signal in the small intestine, what happens downstream?
communicates that info to ToxR which binds to the TCP-ACF element DNA to activate transcription of the colonization virulence factors
What is ToxT and what role does it play?
ToxT is part of the tcp operon and it activates expression of the tcp promoter (activating toxT transcription)
it controls most ToxR regulon genes including the tcp operon
True or false: toxT autoregulates
True
True or false: toxT activates CTX operon
true
What 3 things are required by V. cholera virulence?
1) the chromosome (toxRS operon)
2) pathogenicity island (TCP-ACF)
3) temperate or lysogenic bacteriophage (CTX phage carrying ctxAB)
True or false: Tox R and S are in the ToxR regulon
FALSE
