Name: __________________________ Date:____________
BIO2073: Microbiology Lab
Group Activity
Biochemical Tests: Phenol Red Fermentation Broth and Catalase Test
1. Phenol Red Broth: In your Data file, you have results for 8 different unknowns, labeled A-H. Each one has been inoculated into PR broth containing (1) Dextrose (aka, glucose) and (2) sucrose. Record the results in the table below.
Sample
Carbohydrate Source
Result (A/G, A/-, -/-, or K)
Control
Dextrose
Sucrose
A
Dextrose
Sucrose
B
Dextrose
Sucrose
C
Dextrose
Sucrose
D
Dextrose
Sucrose
E
Dextrose
Sucrose
F
Dextrose
Sucrose
G
Dextrose
Sucrose
H
Dextrose
Sucrose
6. If you tested an organism using the Phenol Red glucose test, and it was positive, could you accurately conclude that your organism would also test positive using sucrose instead? Why or why not?
____________________________________________________________________________________
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7. a. Write down the equation for the chemical reaction that is occurring during the catalase test:
b. In the catalase test, the formation of bubbles is considered a positive result, indicating the organism produces the enzyme catalase. What product of the reaction is responsible for the formation of bubbles?
____________________________________________________________________________________
8. Name a medically significant microbe that would test positive for coagulase:
_________________________________________________________________
*Bonus question on next page!
Bonus! Imagine that your coagulase test was negative with the slide test, but positive for the tube test. What is the most likely explanation for this observation? (Assume that we can rule out human error.)
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