Exercise 13
LABORATORY REPORT
Carbohydrate Catabolism and
Other Metabolism Tests
Name __________________________
Period __________
Date
__________
Purpose: ________________________________________________________
OF – Glucose
Color
Organism
Open
Tube
Fermenter (F),
Oxidizer (O),
Non-Utilizer (N)
Plugged
Tube
Motile?
+/-
Pseudomonas
Bacillus subtilis
E. coli
TSI Slant:
NOTE: For Slant & Butt color: NC = No change, >R = Redder, Y = Yellow
Organism
Growth
(= / + )
Slant
Color
Butt
Color
Black
precip
?
(B /NB)
Gas bubble?
(Gas/No gas)
NB
No
Result, i.e.:
K/A H2S+
List the sugar(s)
utilized
Pseudomonas
Bacillus
E. coli
Example
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NC
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Y
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K/A H2S-
Glucose only,
then peptones
Questions:
1. Starch hydrolysis:
a. Which organism(s) gave a positive test?
b. Describe how you determine a positive test.
c. What would be found in the clear area of the starch agar that would not be found in the blue
area after the addition of iodine? Be specific. It should link to the reaction that causes a clear
area.
d. How can you tell that amylase is an exoenzyme and not an endoenzyme?
2. OF-Glucose Deeps. How can you tell whether an organism***Be specific.***All three answers
should be distinctly different.***
a. Oxidizes glucose
b. Ferments glucose?
c. Doesn’t use glucose?
d. If an organism grows in the OF-glucose medium that is exposed to the air, is the organism
oxidizing or fermenting glucose. Explain your answer.
3. Why is it important to first determine if growth occurred in a differential medium, such as starch agar,
before examining the plate for starch hydrolysis?
4. Rate the relative ease of telling if the following are pure (all one species) by visually inspecting it
without a microscope. Rank from 1 (easiest to determine purity) to 4 (hardest to determine)
Broth_____
Slant____
Deep ____
Plate _____
5. Based on this and previous labs, list three situations when it would be preferable to use a needle
rather than loop to inoculate a culture.
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Critical Thinking
1. Some microbes metabolized the peptone in the OF-glucose medium and the indicator turned
darker green/blue, indicating alkaline products. What alkaline product was produced?
Hint: What are the monomers that combine to make proteins and peptones? What part of the
monomer would be alkaline when by itself. (Compare the monomer name to functional groups
from Organic Chemistry.)
2. How can organisms that don’t use starch grow on a starch plate? (What else does the starch agar
have in it?)
3. Locate the H+ and OH – ions from the water molecule that was split (hydrolyzed) in this reaction,
showing esculin hydrolysis. Circle the areas where the ions were added.
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