MICROBIOLOGY LAB FINAL EXAM QUESTIONS
AND ANSWERS TESTED AND APPROVED!!!
Selective media can be useful in isolating bacteria. Mannitol salt agar is
selective because of its _________.
a. pH
b. mannitol
c. salt content
d. sugar content
e. phenol red -- ANSWER--c. salt content
The reason that Staphylococcus aureus turns yellow on MSA is that _________.
a. The microbes have fermented lactose
b. The microbes have fermented mannitol
c. The microbes are resistant to phenol red
d. The microbes are salt-tolerant
e. The microbes are resistant to eosin and methylene blue -- ANSWER--b.
The microbes have fermented mannitol
A pure culture consists of which of the following?
a. One streak
b. One species of microbe
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,c. Similar Gram stain reactions
d. One genus of microbe
e. Turbidity -- ANSWER--b. One species of microbe
Eosin methylene blue (EMB) media are selective because of ___________.
a. The agar
b. The pH
c. Mannitol
d. The dyes
e. Phenol red -- ANSWER--d. The dyes
Which of the following media are NOT selective or differential?
a. EMB media
b. MSA media
c. Nutrient agar
d. None of these are both selective and differential media
e. All of these are both selective and differential media -- ANSWER--a.
EMB media
Bacteria with an optimum growth temperature of 37 degrees Celsius are
__________. a. Thermophiles
b. Hyperthermophiles
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,c. Psychrophiles
d. Heat resistant
e. Mesophiles -- ANSWER--e. Mesophiles
Which one of the following is FALSE about a simple, direct stain?
a. It is used to determine morphology
b. It usually involves a basic stain
c. It uses a negatively charged atmosphere
d. It uses one stain
e. It colors the cell -- ANSWER--c. It uses a negatively charged atmosphere
The following steps done to make a direct stain of a smear. Which step must be
done first? a. Heat-fix
b. Air-dry
c. Blot-dry
d. Stain
e. The order doesn't matter -- ANSWER--b. Air-dry
The following reagents are used in the Gram stain. Which reagent is used in the
first step? a. Crystal violet
b. Ethanol
c. Safranin
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, d. Iodine
e. They can be used in any order -- ANSWER--a. Crystal violet
Which of the following is an example of an acid-fast pathogen?
a. Staphylococcus aureus
b. Escherichia coli
c. Mycobacterium leprae
d. Streptococcus pyogenes
e. Candida albicans -- ANSWER--c. Mycobacterium leprae
The purpose of acid alcohol in the acid-fast stain is to _________.
a. Kill bacteria
b. Stain the cells
c. Stain Gram-negative cells
d. Decolorize non-acid-fast cells
e. Disinfect the slide -- ANSWER--d. Decolorize non-acid-fast cells
Malachite green and safranin are used in the endospore stain. The endospores
will be _________.
a. Green and red
b. Colorless
c. Green
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AND ANSWERS TESTED AND APPROVED!!!
Selective media can be useful in isolating bacteria. Mannitol salt agar is
selective because of its _________.
a. pH
b. mannitol
c. salt content
d. sugar content
e. phenol red -- ANSWER--c. salt content
The reason that Staphylococcus aureus turns yellow on MSA is that _________.
a. The microbes have fermented lactose
b. The microbes have fermented mannitol
c. The microbes are resistant to phenol red
d. The microbes are salt-tolerant
e. The microbes are resistant to eosin and methylene blue -- ANSWER--b.
The microbes have fermented mannitol
A pure culture consists of which of the following?
a. One streak
b. One species of microbe
Page 1 of 206
,c. Similar Gram stain reactions
d. One genus of microbe
e. Turbidity -- ANSWER--b. One species of microbe
Eosin methylene blue (EMB) media are selective because of ___________.
a. The agar
b. The pH
c. Mannitol
d. The dyes
e. Phenol red -- ANSWER--d. The dyes
Which of the following media are NOT selective or differential?
a. EMB media
b. MSA media
c. Nutrient agar
d. None of these are both selective and differential media
e. All of these are both selective and differential media -- ANSWER--a.
EMB media
Bacteria with an optimum growth temperature of 37 degrees Celsius are
__________. a. Thermophiles
b. Hyperthermophiles
Page 2 of 206
,c. Psychrophiles
d. Heat resistant
e. Mesophiles -- ANSWER--e. Mesophiles
Which one of the following is FALSE about a simple, direct stain?
a. It is used to determine morphology
b. It usually involves a basic stain
c. It uses a negatively charged atmosphere
d. It uses one stain
e. It colors the cell -- ANSWER--c. It uses a negatively charged atmosphere
The following steps done to make a direct stain of a smear. Which step must be
done first? a. Heat-fix
b. Air-dry
c. Blot-dry
d. Stain
e. The order doesn't matter -- ANSWER--b. Air-dry
The following reagents are used in the Gram stain. Which reagent is used in the
first step? a. Crystal violet
b. Ethanol
c. Safranin
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, d. Iodine
e. They can be used in any order -- ANSWER--a. Crystal violet
Which of the following is an example of an acid-fast pathogen?
a. Staphylococcus aureus
b. Escherichia coli
c. Mycobacterium leprae
d. Streptococcus pyogenes
e. Candida albicans -- ANSWER--c. Mycobacterium leprae
The purpose of acid alcohol in the acid-fast stain is to _________.
a. Kill bacteria
b. Stain the cells
c. Stain Gram-negative cells
d. Decolorize non-acid-fast cells
e. Disinfect the slide -- ANSWER--d. Decolorize non-acid-fast cells
Malachite green and safranin are used in the endospore stain. The endospores
will be _________.
a. Green and red
b. Colorless
c. Green
Page 4 of 206
