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MCB2010L FINAL EXAM WITH CORRECT ACTUAL
QUESTIONS AND CORRECTLY WELL DEFINED
ANSWERS LATEST 2024 – 2025 ALREADY GRADED A+
What is fluid thioglycollate broth (FTB)? - (answers)It is prepared as a basic
medium or with a variety of substances, depending on the needs of the organism
being cultivated. It is appropriate for a broad variety of aerobic and anaerobic,
and fastidious (requiring specific nutrients to grow) and non fastidious organisms.
Well adapted for strict anaerobes and microaerophiles.
What are the key components of FTB? - (answers)Yeast extract, pancreatic digest
of casein, dextrose, sodium thioglycollate, L-cystine, and resazurin.
-yeast extract and casein provide nutrients
-sodium thioglycollate and L-cystine reduce oxygen to water
-resazurin is an indicator of oxygen
What purpose does resazurin dye serve in FTB? - (answers)Oxygen indicator. Pink
when oxidized, colorless when reduced.
What is the application of FTB? - (answers)Can be modified to promote growth of
a wide variety of fastidious to non fastidious microorganisms. It can be used to
illustrate microbial growth representing all levels of oxygen tolerance. However, it
generally is associated with the cultivation of anaerobic and microaerophilic
bacteria.
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Why is it preferred to use fresh FTB medium over old medium? - (answers)Oxygen
removed during autoclaving will diffuse back into the medium as the tubes cool to
room temperature. This produces a gradient of concentrations from aerobic
(comparable to air) at the top to anaerobic at the bottom. Fresh media will
appear clear to straw coloured with a pink region at the top, where the dye has
become oxidized. The use of old medium will cause the aerobic region of the tube
to grow, indicating widespread oxidation throughout the tube.
Where would you expect to see growth on FTB medium of a strict aerobe,
anaerobe, microaerophile, facultative anaerobe, and an aerotolerant anaerobe? -
(answers)-Strict aerobe: at the top of the broth, where oxygen is abundant
-Anaerobe: at the bottom of the broth, where oxygen is not present
-Microaerophile: in the middle of the broth where oxygen is present, but not in
large amounts
-Facultative anaerobe: concentrated at the top (grows best when most oxygen is
present), but spread throughout (can grow anaerobically)
-Aerotolerant anaerobe: growth relatively evenly throughout (anaerobic, but
tolerates oxygen presence)
Consider resazurin dye. Considering the major application of this medium, which
is more desirable, a thick coloured or a thin coloured band? - (answers)A thin
coloured band would be more desirable, as it would indicate that the medium is
more fresh. The older the medium, the more oxidation occurs within the media,
creating the indicator band to expand. Certain bacteria will not be able to grow or
the results of their growth will become skewed.
Where is the resazurin located in the broth column? - (answers)At the very top of
the broth, forming a band.
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Why is the FTB broth pink at the surface of the medium? - (answers)This is where
the most oxygen is present.
Which type of organism would most likely be affected negatively by the use of old
FTB media? - (answers)Strict (obligate) anaerobes; these organisms are inhibited
by the presence of oxygen, therefore an abundance of oxygen in the tube may
produce limited growth by these organisms.
Which type of organism would most likely be positively affected by the use of old
FTB media? - (answers)Strict (obligate) aerobes; the abundance of oxygen in the
media will provide a tremendous advantage to these organism's growth, as they
need sufficient amounts of oxygen to produce.
Which type of organism would be least affected by the use of old FTB media? -
(answers)Aerotolerant anaerobes; these bacteria continue their production
anaerobically in the presence of oxygen. Oxygen presence will neither inhibit, nor
fuel their growth.
What is the GasPak Anaerobic System? - (answers)A plastic jar in which we create
anaerobic, microaerophilic, or CO2 enriched conditions, depending on the specific
needs of the bacteria being cultivated.
What components are required for the anaerobic jar? - (answers)Chemical gas
generator packet containing sodium borohydride and sodium bicarbonate, and a
paper indicator strip saturated in methylene blue and resazurin. Palladium acts as
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a catalyst for the reaction that will produce the necessary conditions within the
jar.
What is the purpose of the indicator strip? How is oxygen presence indicated? -
(answers)To confirm the presence or absence of oxygen within the jar. Methylene
blue and resazurin are colorless when reduced, but are blue and pink,
respectively, when oxidized.
What does the gas generator packet do within the anaerobic jar? -
(answers)Water is added to the envelope. Sodium borohydride and sodium
bicarbonate react with the water to produce hydrogen and carbon dioxide gases.
Palladium catalyzes a reaction between hydrogen and free oxygen in the jar to
produce water.
How long does it take for the gas generator packet to create anaerobic
conditions? What is the evidence of this? - (answers)Removal of the free oxygen
produces anaerobic conditions in the jar in approximately one hour; this is
evidenced by the white indicator strip and moisture inside of the jar.
Suppose that after incubation, you examine the jar before opening it and see that
the methylene blue strip is blue (or the resazurin strip is pink). What would you
guess the internal environment to be- aerobic or anaerobic? - (answers)Aerobic;
the indicator strips should be white when within the jar, representing an
anaerobic environment. If these strips are oxidized, they change colour, indicating
the presence of oxygen within the system.
Suppose that after incubation, you examine the jar before opening it and see that
the methylene blue strip is blue (or the resazurin strip is pink). How would you
MCB2010L FINAL EXAM WITH CORRECT ACTUAL
QUESTIONS AND CORRECTLY WELL DEFINED
ANSWERS LATEST 2024 – 2025 ALREADY GRADED A+
What is fluid thioglycollate broth (FTB)? - (answers)It is prepared as a basic
medium or with a variety of substances, depending on the needs of the organism
being cultivated. It is appropriate for a broad variety of aerobic and anaerobic,
and fastidious (requiring specific nutrients to grow) and non fastidious organisms.
Well adapted for strict anaerobes and microaerophiles.
What are the key components of FTB? - (answers)Yeast extract, pancreatic digest
of casein, dextrose, sodium thioglycollate, L-cystine, and resazurin.
-yeast extract and casein provide nutrients
-sodium thioglycollate and L-cystine reduce oxygen to water
-resazurin is an indicator of oxygen
What purpose does resazurin dye serve in FTB? - (answers)Oxygen indicator. Pink
when oxidized, colorless when reduced.
What is the application of FTB? - (answers)Can be modified to promote growth of
a wide variety of fastidious to non fastidious microorganisms. It can be used to
illustrate microbial growth representing all levels of oxygen tolerance. However, it
generally is associated with the cultivation of anaerobic and microaerophilic
bacteria.
,2|Page
Why is it preferred to use fresh FTB medium over old medium? - (answers)Oxygen
removed during autoclaving will diffuse back into the medium as the tubes cool to
room temperature. This produces a gradient of concentrations from aerobic
(comparable to air) at the top to anaerobic at the bottom. Fresh media will
appear clear to straw coloured with a pink region at the top, where the dye has
become oxidized. The use of old medium will cause the aerobic region of the tube
to grow, indicating widespread oxidation throughout the tube.
Where would you expect to see growth on FTB medium of a strict aerobe,
anaerobe, microaerophile, facultative anaerobe, and an aerotolerant anaerobe? -
(answers)-Strict aerobe: at the top of the broth, where oxygen is abundant
-Anaerobe: at the bottom of the broth, where oxygen is not present
-Microaerophile: in the middle of the broth where oxygen is present, but not in
large amounts
-Facultative anaerobe: concentrated at the top (grows best when most oxygen is
present), but spread throughout (can grow anaerobically)
-Aerotolerant anaerobe: growth relatively evenly throughout (anaerobic, but
tolerates oxygen presence)
Consider resazurin dye. Considering the major application of this medium, which
is more desirable, a thick coloured or a thin coloured band? - (answers)A thin
coloured band would be more desirable, as it would indicate that the medium is
more fresh. The older the medium, the more oxidation occurs within the media,
creating the indicator band to expand. Certain bacteria will not be able to grow or
the results of their growth will become skewed.
Where is the resazurin located in the broth column? - (answers)At the very top of
the broth, forming a band.
,3|Page
Why is the FTB broth pink at the surface of the medium? - (answers)This is where
the most oxygen is present.
Which type of organism would most likely be affected negatively by the use of old
FTB media? - (answers)Strict (obligate) anaerobes; these organisms are inhibited
by the presence of oxygen, therefore an abundance of oxygen in the tube may
produce limited growth by these organisms.
Which type of organism would most likely be positively affected by the use of old
FTB media? - (answers)Strict (obligate) aerobes; the abundance of oxygen in the
media will provide a tremendous advantage to these organism's growth, as they
need sufficient amounts of oxygen to produce.
Which type of organism would be least affected by the use of old FTB media? -
(answers)Aerotolerant anaerobes; these bacteria continue their production
anaerobically in the presence of oxygen. Oxygen presence will neither inhibit, nor
fuel their growth.
What is the GasPak Anaerobic System? - (answers)A plastic jar in which we create
anaerobic, microaerophilic, or CO2 enriched conditions, depending on the specific
needs of the bacteria being cultivated.
What components are required for the anaerobic jar? - (answers)Chemical gas
generator packet containing sodium borohydride and sodium bicarbonate, and a
paper indicator strip saturated in methylene blue and resazurin. Palladium acts as
, 4|Page
a catalyst for the reaction that will produce the necessary conditions within the
jar.
What is the purpose of the indicator strip? How is oxygen presence indicated? -
(answers)To confirm the presence or absence of oxygen within the jar. Methylene
blue and resazurin are colorless when reduced, but are blue and pink,
respectively, when oxidized.
What does the gas generator packet do within the anaerobic jar? -
(answers)Water is added to the envelope. Sodium borohydride and sodium
bicarbonate react with the water to produce hydrogen and carbon dioxide gases.
Palladium catalyzes a reaction between hydrogen and free oxygen in the jar to
produce water.
How long does it take for the gas generator packet to create anaerobic
conditions? What is the evidence of this? - (answers)Removal of the free oxygen
produces anaerobic conditions in the jar in approximately one hour; this is
evidenced by the white indicator strip and moisture inside of the jar.
Suppose that after incubation, you examine the jar before opening it and see that
the methylene blue strip is blue (or the resazurin strip is pink). What would you
guess the internal environment to be- aerobic or anaerobic? - (answers)Aerobic;
the indicator strips should be white when within the jar, representing an
anaerobic environment. If these strips are oxidized, they change colour, indicating
the presence of oxygen within the system.
Suppose that after incubation, you examine the jar before opening it and see that
the methylene blue strip is blue (or the resazurin strip is pink). How would you
