,BIOD171/BIOD 171 Module 5 Exam | Essential Microbiology
with Lab | Portage Learning | Q & A | 2026/2027 Edition (PDF)
1. The concept of treating all samples, whether known or unknown, as potentially hazardous (or
pathogenic) materials is known as which of the following?
A) Standard precautions
B) Universal precautions
C) Transmission-based precautions
D) Aseptic technique
Correct Answer: Universal precautions
Rationale: Universal precautions is the correct term for treating all human blood and certain body fluids
as infectious, regardless of the perceived status of the source. Standard precautions is a broader term
that combines universal precautions and body substance isolation. Transmission-based precautions are
used for patients with known or suspected infections.
2. Which of the following observations should a researcher note when assessing an unknown microbial
sample? (Select all that apply)
A) Size and shape of the organism
B) Any observable motility
C) Gram status (positive or negative)
D) The presence of any chemical reactions
Correct Answer: Size and shape of the organism; Any observable motility; Gram status (positive or
negative); The presence of any chemical reactions
Rationale: A lab researcher would be certain to note size and shape, any observable motility, Gram
status (positive or negative), the presence of any chemical reactions, changes in color localized to the
organism or surrounding media, and capture images of any characteristics described above.
3. While observing an unknown sample of limited amount, a researcher must determine motility and
Gram status using the same sample. Which should be determined first and why?
,A) Gram status first because motility requires a wet mount
B) Motility first because heat fixation in Gram staining would kill the organism
C) Either can be determined first as both use the same preparation
D) Neither test can be performed with a limited sample
Correct Answer: Motility first because heat fixation in Gram staining would kill the organism
Rationale: Motility requires a wet mount of live organisms, while Gram staining requires heat fixation,
which kills the organism. If Gram staining were performed first, motility could no longer be observed.
4. A facultative anaerobe is a microorganism capable of growth under which conditions?
A) Only in the absence of oxygen
B) Only in the presence of oxygen
C) Both aerobic and anaerobic conditions
D) Neither aerobic nor anaerobic conditions
Correct Answer: Both aerobic and anaerobic conditions
Rationale: A facultative anaerobe is capable of growth under both aerobic (with oxygen) and anaerobic
(without oxygen) conditions. It preferentially uses oxygen when available but can switch to fermentation
or anaerobic respiration when oxygen is absent.
5. As Streptococcus is catalase negative, would it thrive or die in the presence of peroxides? Why?
A) Thrive, because catalase breaks down peroxides
B) Die, because it is unable to break down peroxides
C) Thrive, because peroxides are a nutrient source
D) Die, because catalase produces toxic peroxides
Correct Answer: Die, because it is unable to break down peroxides
, Rationale: Streptococcus is catalase negative, meaning it lacks the enzyme catalase to break down
hydrogen peroxide (peroxides) into water and oxygen. Peroxides would damage the cellular integrity of
Strep, causing lysis or cell death.
6. Which agar plate is most commonly used to culture and identify Streptococcus based on its hemolytic
properties?
A) Chocolate agar
B) EMB agar
C) Blood agar
D) Spirit blue agar
Correct Answer: Blood agar
Rationale: Blood agar is the non-selective yet differential agar plate used to identify and classify
Streptococcus based on its hemolytic properties. Blood agar displays alpha, beta, or gamma hemolysis
patterns, which aid in classification and differentiation.
7. The Lancefield groups are used to subdivide antigenic groups of which type of Streptococcus?
A) Alpha-hemolytic Streptococcus
B) Beta-hemolytic Streptococcus
C) Gamma-hemolytic Streptococcus
D) All of the above
Correct Answer: Beta-hemolytic Streptococcus
Rationale: The Lancefield groupings are used to subdivide beta-hemolytic Streptococcus based on the
carbohydrate composition of their cell wall antigens. Alpha-hemolytic and gamma-hemolytic
Streptococci are not classified using the Lancefield system.
8. The distinctions for Lancefield subgroupings lie in the:
A) Catalase activity
with Lab | Portage Learning | Q & A | 2026/2027 Edition (PDF)
1. The concept of treating all samples, whether known or unknown, as potentially hazardous (or
pathogenic) materials is known as which of the following?
A) Standard precautions
B) Universal precautions
C) Transmission-based precautions
D) Aseptic technique
Correct Answer: Universal precautions
Rationale: Universal precautions is the correct term for treating all human blood and certain body fluids
as infectious, regardless of the perceived status of the source. Standard precautions is a broader term
that combines universal precautions and body substance isolation. Transmission-based precautions are
used for patients with known or suspected infections.
2. Which of the following observations should a researcher note when assessing an unknown microbial
sample? (Select all that apply)
A) Size and shape of the organism
B) Any observable motility
C) Gram status (positive or negative)
D) The presence of any chemical reactions
Correct Answer: Size and shape of the organism; Any observable motility; Gram status (positive or
negative); The presence of any chemical reactions
Rationale: A lab researcher would be certain to note size and shape, any observable motility, Gram
status (positive or negative), the presence of any chemical reactions, changes in color localized to the
organism or surrounding media, and capture images of any characteristics described above.
3. While observing an unknown sample of limited amount, a researcher must determine motility and
Gram status using the same sample. Which should be determined first and why?
,A) Gram status first because motility requires a wet mount
B) Motility first because heat fixation in Gram staining would kill the organism
C) Either can be determined first as both use the same preparation
D) Neither test can be performed with a limited sample
Correct Answer: Motility first because heat fixation in Gram staining would kill the organism
Rationale: Motility requires a wet mount of live organisms, while Gram staining requires heat fixation,
which kills the organism. If Gram staining were performed first, motility could no longer be observed.
4. A facultative anaerobe is a microorganism capable of growth under which conditions?
A) Only in the absence of oxygen
B) Only in the presence of oxygen
C) Both aerobic and anaerobic conditions
D) Neither aerobic nor anaerobic conditions
Correct Answer: Both aerobic and anaerobic conditions
Rationale: A facultative anaerobe is capable of growth under both aerobic (with oxygen) and anaerobic
(without oxygen) conditions. It preferentially uses oxygen when available but can switch to fermentation
or anaerobic respiration when oxygen is absent.
5. As Streptococcus is catalase negative, would it thrive or die in the presence of peroxides? Why?
A) Thrive, because catalase breaks down peroxides
B) Die, because it is unable to break down peroxides
C) Thrive, because peroxides are a nutrient source
D) Die, because catalase produces toxic peroxides
Correct Answer: Die, because it is unable to break down peroxides
, Rationale: Streptococcus is catalase negative, meaning it lacks the enzyme catalase to break down
hydrogen peroxide (peroxides) into water and oxygen. Peroxides would damage the cellular integrity of
Strep, causing lysis or cell death.
6. Which agar plate is most commonly used to culture and identify Streptococcus based on its hemolytic
properties?
A) Chocolate agar
B) EMB agar
C) Blood agar
D) Spirit blue agar
Correct Answer: Blood agar
Rationale: Blood agar is the non-selective yet differential agar plate used to identify and classify
Streptococcus based on its hemolytic properties. Blood agar displays alpha, beta, or gamma hemolysis
patterns, which aid in classification and differentiation.
7. The Lancefield groups are used to subdivide antigenic groups of which type of Streptococcus?
A) Alpha-hemolytic Streptococcus
B) Beta-hemolytic Streptococcus
C) Gamma-hemolytic Streptococcus
D) All of the above
Correct Answer: Beta-hemolytic Streptococcus
Rationale: The Lancefield groupings are used to subdivide beta-hemolytic Streptococcus based on the
carbohydrate composition of their cell wall antigens. Alpha-hemolytic and gamma-hemolytic
Streptococci are not classified using the Lancefield system.
8. The distinctions for Lancefield subgroupings lie in the:
A) Catalase activity
