LAB EXAM #2 Flashcards
Indole is an end product of casein hydrolysis?
False
Yellow color indicates a positive reaction for Citrate utilization.
False- blue
The gas bubble in the Durham tube is hydrogen sulfide released by carbohydrate fermentation.
False
A strict Anaerobe will grow_______ in Thioglycollate agar.
At the bottom
If you did a Gram stain on a culture that came out looking gram negative even though you knew it should be gram positive, which of the following could have caused the misleading results?
- You forgot to add ethanol
- You used too much alcohol during decolorization
For the Oxidative–Fermentative Test, what does it mean when both tubes are Yellow?
Fermentative- Acidic pH
SIM Agar is 3 tests in one tube. What are the tests ?
Sulfur reduction
Indole
Motility
Why do we need to check the fermentation broths twice, at 24 and 48 hours?
Some organisms are fast fermenters and will go after the peptone in the broth after they have fermented the carbohydrates
How does DNase enzyme help bacteria?
Hydrolyzes DNA into small fragments
A strict Aerobe will grow_______ in Thioglycollate agar.
On the surface
For the Oxidative–Fermentative Test, what does it mean the tube with no oil is yellow and the tube with oil is green?
Oxidative
For the Oxidative–Fermentative Test, what does it mean when both tubes are green?
Neither fermenter or an oxidizer
S. aureus:
B. cereus:
E. coli:
Gram + cocci
Gram + rod
Gram - rod
In the motility exp, if your organism reduces the 2, 3, 5- triphenyltetrazolium chloride it is:
Motile, red, and will move away from stab line
If your organism did not reduce the 2,3,5-triphenyltetrazolium chloride and is motile:
Media will be red and hazy/cloudy
If your organism reduced the 2,3,5-triphenyltetrazolium chloride and is non-motile you should see:
A red color in the stab line only
If your organism is gram + and a non-spore forming rod you will need to do:
An acid fast stain
What is the oxygen indicator in the sodium thioglycollate medium?
Controls?
Resazurin
- red/pink when O2 is present
- colorless in the absence of O2
Why don’t we shake the sodium thioglycollate tube?
It will disperse the O2 in the tube
2 experiments using TSA plate?
- Pattern of growth
- Catalase
Hemolysis:
Lysis of RBC
3 types of hemolysis:
- Alpha: partial breakdown of RBC-> green color
- Beta: complete breakdown of RBC-> clearing
- Gamma: No lysis of RBC-> no change
Purpose of catalase test:
To produce the enzyme catalase that degrades hydrogen peroxide to O2 and water
Controls of catalase test:
Positive: Gas bubbles
Negative: No bubbles
Controls for methyl red test?
Positive: red/pink color after adding methyl red
Negative: orange/yellow color after adding methyl red
Controls for voges-proskauer test?
Positive: brick red color after the addition of VP A + VP B
Negative: copper color after the addition of VP A + VP B
Used with Barritt’s Reagents A + B:
VP test
Purpose of MR test:
Detects mixed acid end products of glucose metabolism
Purpose of VP test:
To carry out fermentation of glucose to acetoin and 2, 3 -Butanediol
Controls of fermentation test?
Why?
Positive: Acid/gas and yellow in color due to carbohydrate fermentation and acid production
Negative/basic: no color change or pink color change due to deanimation and the production of ammonia
Purpose of oxidative-fermentative test:
To oxidize or ferment a specific carbohydrate
Why is oil overlaid in 1 of the tubes in the O/F test?
To create an anaerobic environment
Purpose of Simmon’s citrate test?
To utilize citrate as a sole carbon source
Control of Simmon’s citrate test?
Positive: Green to blue
Negative: Yellow or green
Purpose of nitrate test:
To reduce nitrate to nitrite or nitrogen gas
The reduction of nitrate to nitrite is done by the enzyme:
Nitrate reductase
Controls for nitrate test:
Positive: Dark red OR no color change after adding zinc (reagent C)
Negative: no color change or dark red color after adding zinc (reagent C)
Purpose of starch test?
To hydrolyze starch by the production of amylase
Control for starch test:
Positive: Clearing or halo around margins of growth after adding iodine
Purpose of skim milk test?
To hydrolyze casein from milk with the enzyme casease
Control for skim milk test?
Positive: Clearing or halo around margins of growth
Purpose of spirit blue (lipase) test?
To cleave fatty acids from glycerol using the enzyme lipase
Controls of spirit blue (lipase) test?
Positive: Dark blue precipitate (hydrolyzes oil and lowers pH)
Negative: Lightening of plate
Purpose of urea test:
To hydrolyze urea into CO2 and ammonia using the enzyme urease
Control of urea test?
Positive: Pink color
pH indicator of the fermentation test and urea test?
Phenol red
pH indicator of spirit blue (lipase) test?
Tributyrin oil and spirit blue dye
pH indicator of Simmon’s citrate test and O/F test?
Bromthymol blue
Purpose of phenylalanine test?
To deanimate phenylalanine into phenylpyruvic acid and ammonia using the enzyme phenylalanine deaminase
Control of phenylalanine test?
Positive: Green after addition of ferric chloride
Negative: Yellow after addition of ferric chloride
Purpose of DNase test?
To hydrolyze DNA into small fragments using the enzyme DNase
Control of DNase test?
Positive: Clearing around the margins of growth
Indicator of DNase test?
Methyl green
Purpose of decarboxylase test?
To produce decarboxylase enzyme that will remove a carboxyl group from the amino acid
pH indicator of decarboxylase test?
Bromcresol purple
Controls for decarboxylase test?
Positive: Alkaline/purple
Negative: Acidic/yellow
3 amino acids used in decarboxylase test?
Arginine, ornithine, lysine
Why is oil placed over each tube in the decarboxylase test?
To remove external O2 and promote fermentation
Purpose of gelatin test:
To hydrolyze gelatin using the enzyme gelatinase
Control for gelatin test:
Positive: Liquid media
Negative: Solid media
1 drawback of gelatin test?
Gelatin is liquid at temp higher than 28 C so we have to refrigerate tube for 15 minutes to see if it’s truly a liquid or solid
Purpose of indole/SIM test?
To produce the enzyme tryptophanase to hydrolyze tryptophan to produce -> ammonia, indole, and pyruvate
Control of indole/SIM test?
Positive: Red layer on top of media
Detection of indole in the indole/SIM test is due to:
Kovac’s reagant
Purpose of sulfur reduction test?
To reduce sulfur to hydrogen sulfide
Control for sulfur reduction/SIM test?
Positive: Black precipitate
Purpose of durham tube in fermentation test?
To trap any CO2 as a result of fermentation
