Exam 3 Quiz 2 Flashcards
urease test
-look for urease enzyme
urease enzyme
enzyme that hydrolyzes urea
urea
-product of decarboxylation of certain AA
-two products: ammonia and CO2
ammonia
-basic pH: using pH indicator (phenol red)
pH indicator for urease test
-phenol red, will become hot pink if urease present, very distinct
Urease test looks specifically for…
rapid urease producers, to only look for rapid need to be strongly buffered
2 buffers that resist alkalization
-must look at within 24 hours bc slow production could make enough to turn it hot pink in that time period
-cant go into autoclave, needs to be filter sterilized (0.2micro meter)
DNase Test
-deoxyribonuclease
-Agar plate
deoxyribonuclease
-enzyme that catalyzes the depolarization of DNA into small fragments of
agar plate for DNase
-peptide for nutrients
-emulsion of DNA
-methyl green dye
**incubate, if bacteria express DNase then it will fragment the DNA and lose association w methyl green causing zone of clearing
methyl green dye
bind to DNA normally if DNase present loses this ability
Gram - enteric organisms
IMViC tests
IMViC
I=Indle
M=methyl red
V=voges-prokauer
C=citrate
**four different tests
Indole test
-looking for expression of tryptophanase (enzyme that breaks down tryptophan)
3 products of broken down tryptophan
- Indole
- Pyruvate
- Ammonia (pyruvate and ammonia have short 1/2 lives)
SIM media
-sulfur reduction, indole, motility
-look for thiosulfate reductase : makes H2S
-combine with ferrous ammonium sulfate: forms black precipitate
1% tryptone broth
-add kovacs reagent, if detects indole on media it will turn red, red ring means positive result
MR-VP broth
methyl red and voges proskaur, can do in same tube or in seperate tubes
mixed acid fermentation
-acetic
-lactic
-succinic
-formic
-pH indicator: methyl red, if acid produced it stays red: positive result
Butanediol fermentation
-acetoin: precursor to butanediol
-Barri H’s reagent A: alpha napthol
-Barri H’s reagent B: KOH
**if present, red, positive result
in MR-VP results
-organisms cant do both types of fermentation so will not see two positive results in same tube
Simmons citrate agar slant
-synthetic media
-looking for citrate permease
-mineral salts
-sodium citrate: only energy source but grow/no grow is hard to tell
-ammonium ions: included to bias those that grow to produce basic products
-pH indicator: bromothymol blue: pretty blue if basic (positive), still green means negative result
