LAB MIDTERM TESTS Flashcards
identifies bacterium that can ferment glucose
purpose of Carbohydrate (Glucose) Fermentation test:
broth turns YELLOW
positive carbohydrate test
broth stays RED
negative carbohyrate test
phenol red
what acts as a pH indicator in carbohydrate test?
lowers pH below 7 (or 6.8)
carbohydrate test: if a bacterium ferments a sugar, what will happen to the pH of the medium?
determines which fermentation route is used to utilize glucose; detects the production of acids (lowers pH)
purpose of Mixed Acid (MR) test:
RED broth at a pH of 5 or less
pos. MR test
broth stays YELLOW
neg. MR test
Methyl Red
reagent used in MR test
pH of 5 or lower
when does methyl red turn red in the MR test?
determines which fermentation route is used to utilize glucose; detects precursors of Butanediol
purpose of Voges-Proskauer (VP) test:
RED broth
pos. VP test
broth stays YELLOW
neg. VP test
Barritt’s A and Barritt’s B reagent
reagents used in VP test:
precursors of Butanediol
what does Barritt’s A and B reagent detect in VP test?
identifies bacterium that use citrate as a carbon source and form sodium carbonate (Na2CO3)
purpose of Citrate Agar test:
blue agar
pos. Citrate test
green agar
neg. Citrate agar test
bromothymol blue
what acts as pH indicator in Citrate test?
green
citrate test: pH indicator bromothymol blue in a NEUTRAL pH
blue
citrate test: color of bromothyl blue in an ALKALINE pH
identifies bacterium that possess the enzyme catalase (breaks down harmful hydrogen peroxide (HOOH) into water and oxygen
purpose of Catalase test:
break hydrogen peroxide into water and oxygen
what does catalase enzyme do?
bubbles
pos. Catalase test
no bubbles
neg. Catalse test
hydrogen peroxide
reagent used for Catalse test
used to identify bacterium that produce cytochrome c oxidase (part of electron transport system); means they perform aerobic respiration to obtain energy
purpose of Oxidase test:
PURPLE stain on streak
pos. Oxidase test
no color change
neg. Oxidase test
oxidase reagents
reagents used for Oxidase test
aerobic respiration
what type of respiration does a bacterium use if it has cytochrome c oxidase?
identifies bacteria that can hydrolyze starch; produce AMYLASE if they do
purpose of Start Hydrolysis test:
clear zone around bacteria (means starch was DIGESTED); does NOT turn black from iodine
pos. starch hydrolysis test
area around bacteria turns black (means starch was NOT digested)
neg. starch hydrolysis test
Iodine
reagent used for Start Hydrolysis test:
turns areas where starch was NOT digested black and leaves areas where starch WAS digested clear
how does iodine work in the Starch Hydrolysis test?
identifies bacteria than can hydrolyze casein (makes milk white); uses skim milk agar plate
purpose of Casein Hydrolysis test:
agar turns CLEAR
pos. Casein test
no color change of agar
neg. Casein Hydrolysis test
none
reagent used for Casein Hydrolysis test
Sulfide Indole Motility
what does SIM stand for?
identifies bacteria that produce hydrogen sulfide (through agar color)
purpose of H2S (hydrogen sulfide) Production:
BLACK agar
pos. H2S (hydrogen sulfide) Production
no color change
neg. H2S (hydrogen sulfide) Production
none
reagent used for H2S production test:
amylase
if bacteria can hydrolyze starch, what enzyme do they produce?
identifies bacteria that produce indole (indole pyruvic acid); means they are capable of breaking down tryptophan
purpose of Tryptophan Degradation (part of SIM tube test):
Kovac’s reagent turns RED
pos. Tryptophan Production test
Kovac’s reagent remains yellow
neg. Tryptophan Production test
detects the presence of Indole
what does Kovac’s reagent do in the Tryptophan Production test?
tryptophan
what amino acid are bacteria capable of breaking down if they are positive for the Indole test?
identifies bacteria that produce the enzyme Urease and perform Urea Hydrolysis; break down urea into CO2 + ammonia (NH3)
purpose of Urease test:
HOT PINK broth (nikki minaj bby) when pH increase
pos. Urease test
broth remains yellow
neg. Urease test
phenol red
what is used as a pH indicator in Urease test?
8.1
what pH does phenol red turn bright pink in the Urease test?
CO2 + ammonia
produces of urea hydrolysis =
INCREASE pH
if a bacterium produces urease, what happens to the pH of the culture medium?
