MICROBIOLOGY LAB FINAL EXAM WITH
137 QUESTIONS AND CORRECT
ANSWERS RATED A+ 2026/2027
Which of the following are true about the agglutination test? Check all that apply.
a. precipitation reactions are visible with the naked eye
b. the test works best when you are trying to detect a single small molecule
c. latex beads are used to amplify reaction
d. a negative control is not required
a&c
Match the following regarding the MIO test.
-Motility
-Indole test
-Ornithine Decarboxylase a positive reaction is indicated by a red color in the
bottom of the tube
Other Incorrect Match Options:
...
-a positive result is scored if the tube shows turbidity
- a negative test is indicated by the lack of a red ring following reagent addition
-negative result is indicated by the formation of a yellow color
...
-a positive reaction is indicated by the development of a yellow color at the top of
the tube
-a positive reaction is indicated by a red color in the bottom of the tube
-a negative reaction is indicated by the development of a purple color
You test an unknown enteric bacterium in the lactose fermentation test and your
observation is that the tube does not change color after inoculation and
incubation. You can conclude that
a. if tested in a KIA test, the result would be an entirely yellow tube
,b. this must not be an enteric, all enterics ferment lactose
c. this bacterium can ferment glucose but not lactose
d. it would not grow on MacConkey's
c
Enteric bacteria (i.e., those of the family Enterobacteriaceae). Check all that apply
a. include Salmonella and E. coli
b. are a group of physiologically diverse bacteria
c. are all Gram-negative bacilli
d. are all associated with mammalian intestinal tract
e. are facultatively anaerobic and are therefore expected to be catalase-positive.
a, c, & e
Both the Methyl Red and the Voges-Proskauer test for the products of ___?____ .
The first one detects ___?____ products while the second one detects
____?____products.
glucose fermentatoin
acid (or acidic pH)
neutral (or neutral pH)
You colleague inoculated a single tube of lysine decarboxylase broth with an
unknown bacterium exactly as follows:
1) the tube was correctly inoculated with a single colony of the bacterium.
2) the tube was immediately placed in the incubator for the required amount of
time.
After incubation, the tube showed a purple color of the broth. Your colleague
concludes that this microbe is capable of lysine decarboxylation.
What are TWO reasons that this conclusion is not a good one?
1. The colleague omitted overlaying the broth with mineral oil, which could affect
the results.
2. There was no control tube prepared to compare growth and acid production.
,What are three typical reactions types of colonies observed on EMB agar and
what do they indicate?
1. The presence of "fish eye" colonies that appear lighter. These "fish eye"
colonies indicate aerogenes-type bacteria.
2. The growth of lactose fermenting bacteria is indicated by the formation of
dark-colored colonies.
3. Coli-type colonies are indicated by the presence of green sheen. The coli-type
colonies can ferment lactose quickly and precipitate Methylene Blue to form the
green sheen.
Since most of the enterics "look" alike, it is often critical to distinguish them from
each other, although there are less common traits that allow us to distinguish
them. Here is a list of 4 bacteria, using the Microbes Discussed document what
test would you use to identify Klebsiella, Morganella, Citrobacter
Klebsiella= motility
morganella=Phenylalanine test
citrobacter= H2S production
Which of the following is NOT a trait of a useful indicator organism?
a. it survives a very long time in the environment
b. it is easy to detect
c. it does not grow outside its natural environment, GI tracts
d. its natural environment is associated with feces
A
In the Gram stain procedure, what would likely happen if you forgot the iodine
step?
a. the cells would wash off the slide
b.the cells could not get decolorized
, c. cells would probably destain more easily
d. all cells would look Gram positive
c
Viruses <100 nm cannot be viewed with (answer all that apply):
a. All of these-viruses are invisible
b. Transmission electron microscope
c. Scanning electron microscope
d. Bright field light microscope
e. Phase microscope
d&e
Which of the following statements are true about use of the 100X lens using a
light microscope. Answer all that apply.
a. actually touches the slide or coverslip
b. is routinely used when observing gram reactions and shapes of cells.
c. gives a final magnification of 100X
d. allows us to observe sub-cellular components of cells
e. requires the use of oil
a, b, & e
I would use an all purpose medium, such as Yeast Extract Tryptone Glucose
media. I would incubate the plates at 30 degrees C.
good = any all-purpose medium like NA or PCA
bad = pretty much anything else, as they would limit the types of microbes that
could grow
Regarding the API strips, which of the following statements are true? Check all
that apply.
a. one would use the same strips for all categories of bacteria
b. a code is generated and used to match the code of known organisms
c. the tests are read immediately after inoculation
d. the test consists of miniaturized pouches of biochemical tests
b&d
137 QUESTIONS AND CORRECT
ANSWERS RATED A+ 2026/2027
Which of the following are true about the agglutination test? Check all that apply.
a. precipitation reactions are visible with the naked eye
b. the test works best when you are trying to detect a single small molecule
c. latex beads are used to amplify reaction
d. a negative control is not required
a&c
Match the following regarding the MIO test.
-Motility
-Indole test
-Ornithine Decarboxylase a positive reaction is indicated by a red color in the
bottom of the tube
Other Incorrect Match Options:
...
-a positive result is scored if the tube shows turbidity
- a negative test is indicated by the lack of a red ring following reagent addition
-negative result is indicated by the formation of a yellow color
...
-a positive reaction is indicated by the development of a yellow color at the top of
the tube
-a positive reaction is indicated by a red color in the bottom of the tube
-a negative reaction is indicated by the development of a purple color
You test an unknown enteric bacterium in the lactose fermentation test and your
observation is that the tube does not change color after inoculation and
incubation. You can conclude that
a. if tested in a KIA test, the result would be an entirely yellow tube
,b. this must not be an enteric, all enterics ferment lactose
c. this bacterium can ferment glucose but not lactose
d. it would not grow on MacConkey's
c
Enteric bacteria (i.e., those of the family Enterobacteriaceae). Check all that apply
a. include Salmonella and E. coli
b. are a group of physiologically diverse bacteria
c. are all Gram-negative bacilli
d. are all associated with mammalian intestinal tract
e. are facultatively anaerobic and are therefore expected to be catalase-positive.
a, c, & e
Both the Methyl Red and the Voges-Proskauer test for the products of ___?____ .
The first one detects ___?____ products while the second one detects
____?____products.
glucose fermentatoin
acid (or acidic pH)
neutral (or neutral pH)
You colleague inoculated a single tube of lysine decarboxylase broth with an
unknown bacterium exactly as follows:
1) the tube was correctly inoculated with a single colony of the bacterium.
2) the tube was immediately placed in the incubator for the required amount of
time.
After incubation, the tube showed a purple color of the broth. Your colleague
concludes that this microbe is capable of lysine decarboxylation.
What are TWO reasons that this conclusion is not a good one?
1. The colleague omitted overlaying the broth with mineral oil, which could affect
the results.
2. There was no control tube prepared to compare growth and acid production.
,What are three typical reactions types of colonies observed on EMB agar and
what do they indicate?
1. The presence of "fish eye" colonies that appear lighter. These "fish eye"
colonies indicate aerogenes-type bacteria.
2. The growth of lactose fermenting bacteria is indicated by the formation of
dark-colored colonies.
3. Coli-type colonies are indicated by the presence of green sheen. The coli-type
colonies can ferment lactose quickly and precipitate Methylene Blue to form the
green sheen.
Since most of the enterics "look" alike, it is often critical to distinguish them from
each other, although there are less common traits that allow us to distinguish
them. Here is a list of 4 bacteria, using the Microbes Discussed document what
test would you use to identify Klebsiella, Morganella, Citrobacter
Klebsiella= motility
morganella=Phenylalanine test
citrobacter= H2S production
Which of the following is NOT a trait of a useful indicator organism?
a. it survives a very long time in the environment
b. it is easy to detect
c. it does not grow outside its natural environment, GI tracts
d. its natural environment is associated with feces
A
In the Gram stain procedure, what would likely happen if you forgot the iodine
step?
a. the cells would wash off the slide
b.the cells could not get decolorized
, c. cells would probably destain more easily
d. all cells would look Gram positive
c
Viruses <100 nm cannot be viewed with (answer all that apply):
a. All of these-viruses are invisible
b. Transmission electron microscope
c. Scanning electron microscope
d. Bright field light microscope
e. Phase microscope
d&e
Which of the following statements are true about use of the 100X lens using a
light microscope. Answer all that apply.
a. actually touches the slide or coverslip
b. is routinely used when observing gram reactions and shapes of cells.
c. gives a final magnification of 100X
d. allows us to observe sub-cellular components of cells
e. requires the use of oil
a, b, & e
I would use an all purpose medium, such as Yeast Extract Tryptone Glucose
media. I would incubate the plates at 30 degrees C.
good = any all-purpose medium like NA or PCA
bad = pretty much anything else, as they would limit the types of microbes that
could grow
Regarding the API strips, which of the following statements are true? Check all
that apply.
a. one would use the same strips for all categories of bacteria
b. a code is generated and used to match the code of known organisms
c. the tests are read immediately after inoculation
d. the test consists of miniaturized pouches of biochemical tests
b&d
