MCB2010L FINAL EXAM 2025
QUESTIONS AND ANSWERS
What is fluid thioglycollate broth (FTB)? - ANS 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? - ANS 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
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,What purpose does resazurin dye serve in FTB? - ANS Oxygen indicator. Pink when oxidized,
colorless when reduced.
What is the application of FTB? - ANS 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.
Why is it preferred to use fresh FTB medium over old medium? - ANS 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? - ANS -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
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,-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? - ANS 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? - ANS At the very top of the broth,
forming a band.
Why is the FTB broth pink at the surface of the medium? - ANS This is where the most
oxygen is present.
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, Which type of organism would most likely be affected negatively by the use of old FTB media? -
ANS 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? -
ANS 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? -
ANS 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? - ANS 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? - ANS Chemical gas generator packet
containing sodium borohydride and sodium bicarbonate, and a paper indicator strip saturated
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QUESTIONS AND ANSWERS
What is fluid thioglycollate broth (FTB)? - ANS 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? - ANS 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
COPYRIGHT © 2025 FYNDLAY ALL RIGHTS RESERVED 1
,What purpose does resazurin dye serve in FTB? - ANS Oxygen indicator. Pink when oxidized,
colorless when reduced.
What is the application of FTB? - ANS 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.
Why is it preferred to use fresh FTB medium over old medium? - ANS 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? - ANS -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
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,-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? - ANS 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? - ANS At the very top of the broth,
forming a band.
Why is the FTB broth pink at the surface of the medium? - ANS This is where the most
oxygen is present.
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, Which type of organism would most likely be affected negatively by the use of old FTB media? -
ANS 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? -
ANS 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? -
ANS 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? - ANS 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? - ANS Chemical gas generator packet
containing sodium borohydride and sodium bicarbonate, and a paper indicator strip saturated
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