BIOL271: Microbiology w/Lab
2026 – 2027 | Portage Learning
Module 4: Microbial Growth — Universal, Selective and Differential Growth Media
Exam Review | LockDown Browser
By PortageMaster
Question 1
Differential media is best suited for distinguishing between two similar species of bacteria. True or
False?
• ✓ True
• False
Correct Answer: True
Feedback: Differential media use color/visual changes (e.g., fermentation indicators) to distinguish
closely related species growing on the same plate.
Question 2
What is differential media?
✓ Answer: Media that helps to distinguish between two or more related species of
microbes — typically through color or biochemical reaction.
Feedback: All organisms grow on differential media, but they look different (e.g., MacConkey
distinguishes lactose fermenters from non-fermenters).
Question 3
What is selective media?
✓ Answer: Media that promotes the growth of particular microbes while restricting the
growth of others.
Feedback: Selective media contain inhibitors (salts, dyes, antibiotics) to suppress unwanted
organisms.
Question 4
What is growth media?
✓ Answer: Media designed to support microbial growth in general (not selective or
differential).
Feedback: Also called “universal” or “general-purpose” media (e.g., LB agar, nutrient agar).
, Question 5
A researcher must determine which of two vials contains E. coli and which contains Salmonella.
Both are Gram-negative but only one can ferment lactose. Which media is best suited?
• Growth Media
• Selective Media
• ✓ Differential Media
• Non-selective and non-differential media
Correct Answer: Differential Media
Feedback: Differential media (e.g., MacConkey) distinguish lactose fermenters (E. coli, pink colonies)
from non-fermenters (Salmonella, colorless).
Question 6
What are the requirements of a fastidious microbe?
✓ Answer: A fastidious microbe has complex, specific growth requirements; without
those nutrients, it will not grow. Enriched media must contain the specific nutrients
needed to support it.
Feedback: Examples: Haemophilus influenzae (needs hemin + NAD), Neisseria meningitidis
(chocolate agar).
Question 7
LB agar is classified as selective, non-differential media. True or False?
• True
• ✓ False
Correct Answer: False
Feedback: LB agar is non-selective and non-differential — it’s a general-purpose growth medium.
Question 8
LB agar is classified as non-selective, differential media. True or False?
• True
• ✓ False
Correct Answer: False
Feedback: LB is neither selective nor differential. It supports broad microbial growth without
distinguishing species.
2026 – 2027 | Portage Learning
Module 4: Microbial Growth — Universal, Selective and Differential Growth Media
Exam Review | LockDown Browser
By PortageMaster
Question 1
Differential media is best suited for distinguishing between two similar species of bacteria. True or
False?
• ✓ True
• False
Correct Answer: True
Feedback: Differential media use color/visual changes (e.g., fermentation indicators) to distinguish
closely related species growing on the same plate.
Question 2
What is differential media?
✓ Answer: Media that helps to distinguish between two or more related species of
microbes — typically through color or biochemical reaction.
Feedback: All organisms grow on differential media, but they look different (e.g., MacConkey
distinguishes lactose fermenters from non-fermenters).
Question 3
What is selective media?
✓ Answer: Media that promotes the growth of particular microbes while restricting the
growth of others.
Feedback: Selective media contain inhibitors (salts, dyes, antibiotics) to suppress unwanted
organisms.
Question 4
What is growth media?
✓ Answer: Media designed to support microbial growth in general (not selective or
differential).
Feedback: Also called “universal” or “general-purpose” media (e.g., LB agar, nutrient agar).
, Question 5
A researcher must determine which of two vials contains E. coli and which contains Salmonella.
Both are Gram-negative but only one can ferment lactose. Which media is best suited?
• Growth Media
• Selective Media
• ✓ Differential Media
• Non-selective and non-differential media
Correct Answer: Differential Media
Feedback: Differential media (e.g., MacConkey) distinguish lactose fermenters (E. coli, pink colonies)
from non-fermenters (Salmonella, colorless).
Question 6
What are the requirements of a fastidious microbe?
✓ Answer: A fastidious microbe has complex, specific growth requirements; without
those nutrients, it will not grow. Enriched media must contain the specific nutrients
needed to support it.
Feedback: Examples: Haemophilus influenzae (needs hemin + NAD), Neisseria meningitidis
(chocolate agar).
Question 7
LB agar is classified as selective, non-differential media. True or False?
• True
• ✓ False
Correct Answer: False
Feedback: LB agar is non-selective and non-differential — it’s a general-purpose growth medium.
Question 8
LB agar is classified as non-selective, differential media. True or False?
• True
• ✓ False
Correct Answer: False
Feedback: LB is neither selective nor differential. It supports broad microbial growth without
distinguishing species.
