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Microbiology Quiz
Basic Lab Tests
FYI, in this quiz there may be words used such as slant, but the photo doesn’t show
the media as a slant. Therefore, just think about what you use in your lab, and
relate that to what you are seeing here.
Photos have been “borrowed” from the internet. If they are yours, please e-mail your URL so
that I can give you credit.
Fun2Care@yahoo.com
Also, most information was taken from Alfred E. Benson’s Microbiology Applications, Short
Version, 9th Edition
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In a Gram stain, what are
the positive and negative results?
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In a Gram stain, what are
the positive and negative results?
Positive: Purple
Negative: Pink
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In a spore stain, what are
the positive and negative results?
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In a spore stain,what are
the positive and negative results?
Positive: Green spores
Negative: No spores (pink)
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In a acid-fast stain,what are
the positive and negative results?
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In a acid-fast stain,what are
the positive and negative results?
Positive: Pink
Negative: Blue
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What is this? What do the results reveal?
http://faculty.southwest.tn.edu/bdrake/Microbiology%20Pictures.htm
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What is this? What do the results reveal?
Motility Test Media - MTM
Negative for Motility
Growth is confined to
the stab area.
Positive for Motility
Growth is radiating
from the stab area,
cloudiness is present
http://faculty.southwest.tn.edu/bdrake/Microbiology%20Pictures.htm
To test if the organism is motile, stab a
depth of 75% of the media and incubate
24-48 hours at the best growth
temperature already decided.
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What is this? What do the results reveal?
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What is this? What do the results reveal?
Gelatin Liquefaction - Nutrient Gelatin
Negative result:Solid in ice bath or
refrigerator after 5
minutes.
Positive result:
Liquid in ice bath or
refrigerator after 5
minutes.
Stab straight to bottom with an inoculating needle.
Put in ice bath or refrigerator for 5 minutes, read
results. If negative, reincubate up to 30 days.
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What is this? What do the results reveal?
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What is this? What do the results reveal?
Phenylalanine Deaminase - Phenylalanine agar slant (PA)
Positive result
Green slant in
0-10 minutes
Streak slant with inoculator,
After incubation time, use 5
drops of phenalalanine reagent.
Negative result
Yellow slant after
5-10 minutes
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What is this? What do the results reveal?
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What is this? What do the results reveal?
Glucose, Lactose or Mannitol Fermentation Phenol Red, Glucose, Lactose Mannitol Broth
Positive Result:
Negative Result:
Yellow
(positive for acid)
Red-pink
(negative for acid)
Bubbles
(positive for gas)
No bubbles
(negative for gas)
Use Durham tube to test for gas, incubate 24-48
hrs. Reincubate negative results up to 30 days.
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What is this? What do the results reveal?
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What is this? What do the results reveal?
Methyl Red Test
Positive Result
Negative Result
After incubating for 2-5 days, add 3-4
drops of Methyl Red reagent.
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What is this? What do the results reveal?
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What is this? What do the results reveal?
Urea hydrolysis - Urea broth
Positive Result
Negative Result
After heavy inoculation,
incubate up to 30 days.
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What is this? What do the results reveal?
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What is this? What do the results reveal?
Starch hydrolysis - Starch agar plate (SA)
Positive Result
Clear zone
Negative Result
Dark zone
After incubating 24-48 hrs, add
grams iodine over growth.
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What is this? What do the results reveal?
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What is this? What do the results reveal?
Citrate utilization - Simmon’s citrate agar slant (S/C)
Negative Result
Positive Result
Uses citrate as
sole carbon
source
Streak slant and stab butt, Incubate
up to 30 days.
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What is this? What do the results reveal?
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What is this? What do the results reveal?
Tryptophan hydrolysis (indole) - Tryptone broth
Positive Result
Red ring
Negative Result
Yellow ring
10 drops of Kovac’s reagent are added
after a 24-48 hour incubation.
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What is this? What do the results reveal?
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What is this? What do the results reveal?
Casein hydrolysis - Skim milk agar plate (SMA)
Positive Result
Clear zone
Negative Result
no zone
Incubate for 24-48 hours
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What is this? What do the results reveal?
http://smccd.net/accounts/case/biol240/vlab.html
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What is this? What do the results reveal?
Litmus reactions - Litmus milk
A = Alkaline
C = Acid
D = Litmus Reduction
E = Peptonization
(Another result may be
coagulation, but is hard too
distinguish in a photo.)
http://smccd.net/accounts/case/biol240/vlab.html
1-5 days incubation time
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What is this? What do the results reveal?
http://biology.uwsp.edu/faculty/TBarta/
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What is this? What do the results reveal?
Hydrogen Sulfide Production - Kliger’s iron agar slant (KIA)
Lactose
Negative
Hydrogen
Sulfide Positive
Black butt
Red Slant
http://biology.uwsp.edu/faculty/TBarta/
Glucose
Positive
Yellow butt
Streak slant for lactose, stab butt for glucose. Incubate 24-48 hours.
Save in refrigerator for new working stock. Lactose positive would
be a yellow slant, and Glucose negative would be a red butt. If it is
H2S+ negative, there will not be any black visible.
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What is this? What do the results reveal?
http://people.uleth.ca/~selibl/Biol3200/BiochTests/
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What is this? What do the results reveal?
Voges-Proskauer Test, aka Acetoin - 1/2 MR-VP media
Voges-Proskauer
Negative
Voges-Proskauer
Positive
Brown color
Red color
http://people.uleth.ca/~selibl/Biol3200/BiochTests/
Add a dropperful of Barritt’s reagent A&B, after
incubating for 5 days, and shake well for 2 hours.
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What is this? What do the results reveal?
http://biology.uwsp.edu/faculty/TBarta/
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What is this? What do the results reveal?
Oxidase Production - Nutrient agar plate (NA)
Oxidase Negative
Oxidase Positive
No black colonies
Black colonies
within 30 minutes
http://biology.uwsp.edu/faculty/TBarta/
After incubation, tamp one oxidase
disk on first quadrant
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What is this? What do the results reveal?
http://faculty.southwest.tn.edu/bdrake/Microbiology%20Pictures.htm
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What is this? What do the results reveal?
Catalase Production - Nutrient agar slant (NA)
Catalase
Production
Negative
Catalase
Production
Positive
No bubbles
Bubbles
http://faculty.southwest.tn.edu/bdrake/Microbiology%20Pictures.htm
After a working stock has been incubated for 3-5
days, add 3 drops of hydrogen peroxide. Make
sure to use an OLD working stock for this test!
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What is this? What do the results reveal?
http://academic.mwsc.edu/jcbaker/images/nitrate%20reduction.jpg
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What is this? What do the results reveal?
Nitrate Reduction - Nitrate agar slant
Postive for
Niatrate
Reduction
Negative for
Nitrate
Reduction
Red color
Clear color
http://academic.mwsc.edu/jcbaker/images/nitrate%20reduction.jpg
Incubate, and then add 3 drops of Nitrate reagents A & B. If a negative
result occurs, confirm the result with zinc dust. Opposite color results will
occur: Clear positive, red negative for nitrate reduction.
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What is this? What do the results reveal?
http://academic.pg.cc.md.us/~kroberts/lecture/web/exoenzymes/lipase.jpg
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What is this? What do the results reveal?
Fat Hydrolysis - Spirit Blue agar plate (SBA)
Postive for
Fat Hydrolysis
Negative for
Fat Hyrolysis
Blue precipitate
No precipitate
http://academic.pg.cc.md.us/~kroberts/lecture/web/exoenzymes/lipase.jpg
Incubate for 24-48 hours.
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Calculate the following dilution:
Using the picture, calculate the
number of cells per milliliter in the
original broth culture if 128 colonies
were counted on plate C1.
A) 128,000,000
B) 130,000,000
C) 1,300,000,000
D) 1,280,000
E) 13,000,000
F) 12,800,000
G) 1,280,000,000
H) 1,300,000
Quoted from a practice practical from
Brookhaven College of DCCCD.
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Calculate the following dilution:
Using the picture, calculate the
number of cells per milliliter in the
original broth culture if 128 colonies
were counted on plate C1.
A) 128,000,000
B) 130,000,000
C) 1,300,000,000
D) 1,280,000
E) 13,000,000
F) 12,800,000
G) 1,280,000,000
H) 1,300,000
Quoted from a practice practical from
Brookhaven College of DCCCD.
The correct answer is: C.
(Remember to round the numbers.)
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Calculate the following dilution:
http://smccd.net/accounts/case/biol230/dilutions2.html#
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Calculate the following dilution:
10-2
10-4
10-5
10-6
http://smccd.net/accounts/case/biol230/dilutions2.html#
The answer is 10-6, or .000001
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Calculate the following dilution:
http://smccd.net/accounts/case/biol230/dilutions2.html#
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Calculate the following dilution:
10-1
10-2
10-3
http://smccd.net/accounts/case/biol230/dilutions2.html#
The answer is 10-3, or .001
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Microbiology Quiz
Basic Lab Tests
Congratulations!!
That’s all for this Microbiology quiz!
Please remember, your instructor may require you to learn more, or
less, of what is on this PowerPoint.
It’s your responsibility to learn what you will be tested on!! (Including
knowing if any errors were made.) Please report any errors to
Fun2Care@Yahoo.com.