BIOD 171 MICROBIOLOGY LAB 1 LAB 9
PRACTICE TEST 2026 QUESTIONS WITH FULL
ANSWERS GRADED A+
◉ What are EMB and McConkey Agar differential for. Answer:
lactose and non-lactose fermenters
◉ How does EMB agar differentiate between lactose and non-lactose
fermenters. Answer: it uses lactose as its medium and when the acid
is fermented, the dyes react on the colony surface, coloring it and
eosin and methylene blue inhibit gram positive bacteria
◉ How does McConkey agar differentiate between lactose and non-
lactose fermenters. Answer: the medium contains a natural pH red
dye and lactose and when lactose is fermented, the clear colonies
become pink on the agar and crystal violet and bile salts inhibit
gram positive bacteria
◉ How many colonies are on a countable plate?. Answer: between
30-300 CFUs
◉ NON-LACTOSE FERMENTERS on the EMB and McConkey agars
appear ____________________.. Answer: Colorless
,◉ On EMB agar, LACTOSE FERMENTERS appear ____________________
(small and large acid production).. Answer: Metallic Green for large
acid production Purple for small acid production
◉ Beta-hemolysis (complete cell lysis). Answer: Clearing around
growth
◉ Alpha-hemolysis (partial cell lysis). Answer: Greening around
growth
◉ Gamma-hemolysis (no cell lysis). Answer: No change in the
medium
◉ Positive Result For Catalase Test. Answer: Bubbles
◉ Negative Result For Catalase Test. Answer: No Bubbles
◉ Positive Result For Coagulase Test. Answer: Plasma forms a clot
◉ Negative Result For Coagulase Test. Answer: Plasma remains
liquid
◉ Positive Result For Gelatin Liquidification Test. Answer: Gelatin
Liquified
, ◉ Negative Result For Gelatin Liquidification Test. Answer: Gelatin
remained solid
◉ What is the importance of the Coagulase Test?. Answer: It
distinguishes Staphylococcus aureus from other Gram positive cocci
◉ What is the enzyme used in the Gelatin Liquidification Test?.
Answer: Gelatinase
◉ Positive Result For Hydrolysis of Milk Protein Test. Answer:
clearing around bacteria
◉ What is the ENZYME used in the Hydrolysis of Milk Protein Test?.
Answer: Casease
◉ What is the SUBSTRATE used in the Hydrolysis of Milk Protein
Test?. Answer: Casein
◉ What does the Phenol Red Fermentation Test determine?.
Answer: Whether the carbohydrate (glucose, lactose, sucrose) was
fermented
PRACTICE TEST 2026 QUESTIONS WITH FULL
ANSWERS GRADED A+
◉ What are EMB and McConkey Agar differential for. Answer:
lactose and non-lactose fermenters
◉ How does EMB agar differentiate between lactose and non-lactose
fermenters. Answer: it uses lactose as its medium and when the acid
is fermented, the dyes react on the colony surface, coloring it and
eosin and methylene blue inhibit gram positive bacteria
◉ How does McConkey agar differentiate between lactose and non-
lactose fermenters. Answer: the medium contains a natural pH red
dye and lactose and when lactose is fermented, the clear colonies
become pink on the agar and crystal violet and bile salts inhibit
gram positive bacteria
◉ How many colonies are on a countable plate?. Answer: between
30-300 CFUs
◉ NON-LACTOSE FERMENTERS on the EMB and McConkey agars
appear ____________________.. Answer: Colorless
,◉ On EMB agar, LACTOSE FERMENTERS appear ____________________
(small and large acid production).. Answer: Metallic Green for large
acid production Purple for small acid production
◉ Beta-hemolysis (complete cell lysis). Answer: Clearing around
growth
◉ Alpha-hemolysis (partial cell lysis). Answer: Greening around
growth
◉ Gamma-hemolysis (no cell lysis). Answer: No change in the
medium
◉ Positive Result For Catalase Test. Answer: Bubbles
◉ Negative Result For Catalase Test. Answer: No Bubbles
◉ Positive Result For Coagulase Test. Answer: Plasma forms a clot
◉ Negative Result For Coagulase Test. Answer: Plasma remains
liquid
◉ Positive Result For Gelatin Liquidification Test. Answer: Gelatin
Liquified
, ◉ Negative Result For Gelatin Liquidification Test. Answer: Gelatin
remained solid
◉ What is the importance of the Coagulase Test?. Answer: It
distinguishes Staphylococcus aureus from other Gram positive cocci
◉ What is the enzyme used in the Gelatin Liquidification Test?.
Answer: Gelatinase
◉ Positive Result For Hydrolysis of Milk Protein Test. Answer:
clearing around bacteria
◉ What is the ENZYME used in the Hydrolysis of Milk Protein Test?.
Answer: Casease
◉ What is the SUBSTRATE used in the Hydrolysis of Milk Protein
Test?. Answer: Casein
◉ What does the Phenol Red Fermentation Test determine?.
Answer: Whether the carbohydrate (glucose, lactose, sucrose) was
fermented
