10.12: Urease Test Procedure — Read

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Urease Test Procedure

Name: _____________________________________________________

Course Section: ______________________________________________

The following activity will teach students how to perform a urease test. Post-inoculation, students will verify urease production.

Materials

Two (2) urea broths.
Test tube rack
2 stock plates
- Stock plates will contain 1 of the following species: Escherichia coli or Micrococcus luteus
Sharpies
Labeling tape
Inoculation loop
Incinerator

Procedure

Day 1

Step 1:

Get into groups of 2.
Obtain 2 urea broth test tubes.
Using labeling tape, label the tube with your name/group name, date, course section, species initials, and test type (e.g., urea).
Using a sterile inoculating loop, aseptically obtain a generous sample of bacteria and mix it into the urea broth. Repeat for both species.
Place the inoculated broths into a test tube rack and incubate for 24 hours at 37 °C.

Day 2

Step 2:

Observe the color of the urea broth.
- pink is positive.
- no color change (i.e., orange) is negative.

In the table below, record your observations for colonies grown in Urea media.

Species

Color Change (Y/N)

Urease (+/-)

Interpretation

Escherichia coli

Micrococcus luteus

1. What is the physiological role of urease in bacteria?

2. What does the color change from orange to pink mean about the pH of the culture?

3. Are there any limitations or potential sources of error when performing the urease test?

4. How does the breath test help diagnose Helicobacter pylori infection?

5. How does Helicobacter pylori survive in the highly acidic environment of the stomach?

Resources

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