Lab #12 Flashcards
Citrate Test
Green ► Blue
= positive
= pH change
= uses citrate
Still Green
= negative
= no pH change
= does not use citrate
Lactose Fermentation Test
purple ► yellow
= positive
= pH change (acidic)
= ferments lactose
Lactose Fermentation Test
still purple
= negative
= no pH change
= does not ferment lactose
Hydrogen Sulfide Production
black precipitate
= positive
= produces H2S
= has cysteine desulfurase
Hydrogen Sulfide Production
no precipitate
= negative
= does not produce H2S
= lacks cysteine desulferase
What is the Principle of the Indole Production Test?
To determine the ability of an organism to catabolize (breaking down) the amino acid tryptophan into indole, pyruvic acid, and ammoniaI
Indole Production tests for the…
presence of the enzyme tryptophanase
Indole Production Test
Formula
tryptophan tryptophanase → indole + pyruvate + NH3
Indole Production Test
Medium
Tryptone broth
♦ Contains tryptophan, which is the substrate for the enzyme tryptophanase
Indole Production Test
What is added after inoculation and incubation for 24-48 hours?
Kovac’s Reagent
Indole Production Test
True or False?
You will not know if the test is positive or negative until the addition of Kovac’s Reagent
True
Indole Production Test
Inoculation and incubation
Red ring in broth
= positive
= has Trp-ase
Indole Production Test
Inoculation and incubation
Yellow ring in broth
= negative
= does not have Trp-ase
Indole Production Test
Enterobacter aerogenes (-) vs. E. coli (+)
Methyl Red Test
Principle
Determine the ability of bacteria to produce large quantities of acid from glucose fermentation
Methyl Red Test
True or False
Some bacteria can ferment glucose to produce a large quantity of acids
True
Methyl Red Test
Test for the presence of the …
multiple enzymes
Methyl Red Test
Medium
Methyl red (MR) broth containing glucose
Methyl Red Test
methyl red is a ___ indicator
pH indicator
Methyl Red Test
Methyl red is red at pH < __
pH < 5
Methyl Red Test
Methyl red is yellow at pH > __
pH > 6
Methyl Red Test
True or False
You will not know if the test is positive or negative until the addition of the indicator
True
Methyl Red Test
Inoculation and incubation
Red
= positive
= pH < 5
= presence of acids
= has necessary enzymes
Methyl Red Test
Inoculation and incubation
Yellow
= negative
= ph > 6
= no acids produces
= lacks necessary enzymes
Klebsiella spp./Enterobacter aerogenes (-) vs. E. coli (+)
Motility Test
True or False
Bacteria can be motile and non-motile
True
Motility Test
Some bacteria use ______ for motility
a. tails
b. wheels
c. flagella (singular flagellum)
d. nitrogen
c. flagella (singular flagellum)
Motility Test
A mobile genus of bacteria is ____
Proteus
Motility Test
Medium
Motility stab
Motility Test
Contains a semi-solid _____
semi-solid gelatin agar
Motility Test
Motile bacteria are __________ from the stab into the agar
a. able to swim away
b. not able to swim away
a. able to swim away
Motility Test
Non-motile bacteria _____ spread from the stab
a. can
b. cannot
b. cannot
Motility Test
Also contains _____ ____ to indicate growth: turns reddish-pink anywhere there is growth
tetrazolium sal
Motility Test
Stab! and incubate
Reddish-pink radiating out from stab
= positive
= bacteria are motile via flagella
Motility Test
Stab! and incubate
Reddish-pink limited to stab area
= negative
= bacteria are non-motile because they lack flagella
Nitrate Reduction
Principle
Determine the ability of an organism to reduce nitrate to nitrites or free nitrogen gas while undergoing anaerobic respiration
Nitrate Reduction
Test for the presence of the enzyme _____
nitratase
Nitrate Reduction
Three possible cases
- nitrate ► nitrite
- nitrate ► nitrite ► nitrogen gas (denitrification)
- no nitrate reduction
Nitrate Reduction
Medium
Nitrate broth
Nitrate Reduction
Reagents
Sulfanilic acid (A)
Alpha naphthylamine (B)
Zinc dust (only if necessary)
Urease Test
Principle
Determine the ability of an organism to break down
urea into ammonia and carbon dioxide
Urease Test
The presence of ammonia drives the pH ____ (i.e. makes
the pH more alkaline/basic)
a. up
b. down
a. up
Urease Test
urease
(NH2)2CO + H2O ————> CO2 + 2NH3
urea
Urease test
Medium
Urea slant
Urease test
Contains a pH indicator that turns ____ when pH shifts to alkaline and ____ when there is no pH change
pink
orange
Urease test
Differentiates between ____ ____ and _____ that cause UTIs from the _____ _____ _____
Differentiates between Proteus (urease+) and pathogens that cause UTIs from the Enterobacteria family (urease-)
Urease test
Inoculate urea slant
Orange ► Pink
= positive
= pH alkaline
= has urease
Urease test
Inoculate urea slant
Still Orange
= negative
= no pH change
= no urease
