,BIOD 171 Module 4 | Practice Q&A | 2026/2027 | Microbiology |
Portage Learning
1. What is the primary purpose of growth (general-purpose) media?
A) To inhibit the growth of unwanted bacteria
B) To distinguish between two similar species of bacteria
C) To simply support microbial growth without restriction
D) To provide specific nutrients for fastidious organisms
Correct Answer: To simply support microbial growth without restriction
Rationale: Growth media is designed to simply support (and not restrict)
microbial growth. It does not contain selective or differential agents.
Selective media inhibits certain organisms, and differential media
distinguishes between species.
2. True or False: Differential media is best suited for distinguishing between
two similar species of bacteria.
A) True
B) False
Correct Answer: True
Rationale: Differential media is designed to distinguish between two similar
species of bacteria based on their metabolic characteristics. Growth media
simply supports growth, and selective media encourages one microbe while
discouraging another.
3. A researcher is asked to determine which of two vials contains Escherichia
coli and which contains Salmonella. Knowing both are Gram-negative while
,only one of them is capable of fermenting lactose, which type of media
would be best suited?
A) Growth media
B) Selective media
C) Differential media
D) Enriched media
Correct Answer: Differential media
Rationale: Differential media such as MacConkey agar incorporates lactose
and a pH indicator, enabling differentiation of lactose fermenters (E. coli,
producing pink colonies) from non-fermenters (Salmonella, producing
colorless colonies).
4. What are the requirements of a fastidious microbe?
A) Only basic nutrients found in minimal media
B) Complex growth requirements requiring enriched media containing
specific essential nutrients
C) Cannot grow at any temperature
D) Grow best on selective media only
Correct Answer: Complex growth requirements requiring enriched media
containing specific essential nutrients
Rationale: Fastidious microbes have complex growth requirements such that
if absent they will not grow and require enriched media containing specific
essential nutrients. They cannot grow on minimal or basic media.
5. True or False: LB agar is classified as a selective, non-differential media.
, A) True
B) False
Correct Answer: False
Rationale: LB (Luria-Bertani) agar is a growth (general-purpose) media, not a
selective media. It supports the growth of many organisms without
restricting any particular type. Selective media contains inhibitors that
suppress certain organisms.
6. What is agar used for in microbiology?
A) As a nutrient source for bacteria
B) To inhibit bacterial growth
C) To provide a solid and even substrate for microbial growth
D) As a pH indicator
Correct Answer: To provide a solid and even substrate for microbial growth
Rationale: Agar is an inert polysaccharide used to solidify liquid media,
creating a stable environment where microbial colonies form discrete units
that can be analyzed and isolated. It is not a nutrient source, inhibitor, or pH
indicator.
7. The polysaccharide-based hardening agent added to LB media to produce
LB agar is derived from what?
A) Bacterial cell wall
B) Seaweed extract
C) Animal collagen
D) Synthetic polymers
Portage Learning
1. What is the primary purpose of growth (general-purpose) media?
A) To inhibit the growth of unwanted bacteria
B) To distinguish between two similar species of bacteria
C) To simply support microbial growth without restriction
D) To provide specific nutrients for fastidious organisms
Correct Answer: To simply support microbial growth without restriction
Rationale: Growth media is designed to simply support (and not restrict)
microbial growth. It does not contain selective or differential agents.
Selective media inhibits certain organisms, and differential media
distinguishes between species.
2. True or False: Differential media is best suited for distinguishing between
two similar species of bacteria.
A) True
B) False
Correct Answer: True
Rationale: Differential media is designed to distinguish between two similar
species of bacteria based on their metabolic characteristics. Growth media
simply supports growth, and selective media encourages one microbe while
discouraging another.
3. A researcher is asked to determine which of two vials contains Escherichia
coli and which contains Salmonella. Knowing both are Gram-negative while
,only one of them is capable of fermenting lactose, which type of media
would be best suited?
A) Growth media
B) Selective media
C) Differential media
D) Enriched media
Correct Answer: Differential media
Rationale: Differential media such as MacConkey agar incorporates lactose
and a pH indicator, enabling differentiation of lactose fermenters (E. coli,
producing pink colonies) from non-fermenters (Salmonella, producing
colorless colonies).
4. What are the requirements of a fastidious microbe?
A) Only basic nutrients found in minimal media
B) Complex growth requirements requiring enriched media containing
specific essential nutrients
C) Cannot grow at any temperature
D) Grow best on selective media only
Correct Answer: Complex growth requirements requiring enriched media
containing specific essential nutrients
Rationale: Fastidious microbes have complex growth requirements such that
if absent they will not grow and require enriched media containing specific
essential nutrients. They cannot grow on minimal or basic media.
5. True or False: LB agar is classified as a selective, non-differential media.
, A) True
B) False
Correct Answer: False
Rationale: LB (Luria-Bertani) agar is a growth (general-purpose) media, not a
selective media. It supports the growth of many organisms without
restricting any particular type. Selective media contains inhibitors that
suppress certain organisms.
6. What is agar used for in microbiology?
A) As a nutrient source for bacteria
B) To inhibit bacterial growth
C) To provide a solid and even substrate for microbial growth
D) As a pH indicator
Correct Answer: To provide a solid and even substrate for microbial growth
Rationale: Agar is an inert polysaccharide used to solidify liquid media,
creating a stable environment where microbial colonies form discrete units
that can be analyzed and isolated. It is not a nutrient source, inhibitor, or pH
indicator.
7. The polysaccharide-based hardening agent added to LB media to produce
LB agar is derived from what?
A) Bacterial cell wall
B) Seaweed extract
C) Animal collagen
D) Synthetic polymers
