BIOD 171 Microbiology Module 6 Exam –
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Which of the following terms describes an organism that requires
oxygen for growth?
A) Facultative anaerobe
B) Obligate anaerobe
C) Obligate aerobe
D) Aerotolerant anaerobe
Answer: C
Rationale: Obligate aerobes strictly require oxygen to survive and
grow because they rely on aerobic respiration to generate ATP.
Facultative anaerobes can grow with or without oxygen, obligate
anaerobes are killed by oxygen, and aerotolerant anaerobes do not
use oxygen but can survive in its presence.
An organism that grows in the presence of oxygen but does not use
it for metabolism is a(n):
A) Microaerophile
B) Aerotolerant anaerobe
C) Obligate aerobe
D) Capnophile
Answer: B
Rationale: Aerotolerant anaerobes can tolerate oxygen and grow in
its presence, but their metabolism is strictly fermentative, meaning
they do not utilize oxygen for ATP production.
Where would you expect to find a microaerophile growing in a
thioglycollate tube?
A) Throughout the entire tube
B) Only at the very top
C) Near the top, but not at the very surface
D) Only at the very bottom
Answer: C
, Rationale: Microaerophiles require oxygen at concentrations lower
than that of atmospheric air (typically 2% to 10%). In a thioglycollate
tube, this oxygen gradient exists just below the surface where the
dye is pink, allowing them to grow exclusively in this narrow band.
Which of the following organisms would most likely be found
growing at the bottom of a thioglycollate tube?
A) Obligate aerobe
B) Facultative anaerobe
C) Obligate anaerobe
D) Microaerophile
Answer: C
Rationale: Thioglycollate medium contains a reducing agent that
removes oxygen, creating an anaerobic environment at the bottom
of the tube. Obligate anaerobes are killed by oxygen and therefore
will only grow in this oxygen-free zone.
A facultative anaerobe is inoculated into a thioglycollate tube. What
pattern of growth would you observe?
A) Growth only at the top
B) Growth only at the bottom
C) Growth throughout the tube, but densest at the top
D) Growth in a band just below the surface
Answer: C
Rationale: Because facultative anaerobes can use oxygen for aerobic
respiration (which yields more ATP), they will grow best at the top
where oxygen is present. However, since they can also ferment in
the absence of oxygen, they will grow throughout the rest of the
tube.
An organism that thrives in extremely high temperatures (above
80°C) is classified as a:
A) Thermophile
B) Hyperthermophile
C) Psychrophile
D) Mesophile
Answer: B
Portage learning
Questions and Answers
With rationales 2026\2027 update
This Exam contains:
Guarantee passing score
Questions and Ansẉers
format set of multiple-choice
Expert-Verified rationales
Verified ẉith trusted textbooks
,───────────────────────────────────────────────────────
─
Which of the following terms describes an organism that requires
oxygen for growth?
A) Facultative anaerobe
B) Obligate anaerobe
C) Obligate aerobe
D) Aerotolerant anaerobe
Answer: C
Rationale: Obligate aerobes strictly require oxygen to survive and
grow because they rely on aerobic respiration to generate ATP.
Facultative anaerobes can grow with or without oxygen, obligate
anaerobes are killed by oxygen, and aerotolerant anaerobes do not
use oxygen but can survive in its presence.
An organism that grows in the presence of oxygen but does not use
it for metabolism is a(n):
A) Microaerophile
B) Aerotolerant anaerobe
C) Obligate aerobe
D) Capnophile
Answer: B
Rationale: Aerotolerant anaerobes can tolerate oxygen and grow in
its presence, but their metabolism is strictly fermentative, meaning
they do not utilize oxygen for ATP production.
Where would you expect to find a microaerophile growing in a
thioglycollate tube?
A) Throughout the entire tube
B) Only at the very top
C) Near the top, but not at the very surface
D) Only at the very bottom
Answer: C
, Rationale: Microaerophiles require oxygen at concentrations lower
than that of atmospheric air (typically 2% to 10%). In a thioglycollate
tube, this oxygen gradient exists just below the surface where the
dye is pink, allowing them to grow exclusively in this narrow band.
Which of the following organisms would most likely be found
growing at the bottom of a thioglycollate tube?
A) Obligate aerobe
B) Facultative anaerobe
C) Obligate anaerobe
D) Microaerophile
Answer: C
Rationale: Thioglycollate medium contains a reducing agent that
removes oxygen, creating an anaerobic environment at the bottom
of the tube. Obligate anaerobes are killed by oxygen and therefore
will only grow in this oxygen-free zone.
A facultative anaerobe is inoculated into a thioglycollate tube. What
pattern of growth would you observe?
A) Growth only at the top
B) Growth only at the bottom
C) Growth throughout the tube, but densest at the top
D) Growth in a band just below the surface
Answer: C
Rationale: Because facultative anaerobes can use oxygen for aerobic
respiration (which yields more ATP), they will grow best at the top
where oxygen is present. However, since they can also ferment in
the absence of oxygen, they will grow throughout the rest of the
tube.
An organism that thrives in extremely high temperatures (above
80°C) is classified as a:
A) Thermophile
B) Hyperthermophile
C) Psychrophile
D) Mesophile
Answer: B
