About this test
What is the purpose of the test?
The purpose is to see if the microbe can use the protein gelatin as a source of carbon and energy for growth. Use of gelatin is accomplished by the enzyme gelatinase .
How is gelatinase activity determined?
A medium containing gelatin is used. The presence of gelatinase is detected by the addition of saturated ammonium sulfate after a streak plate has been allowed to grow overnight. The ammonium sulfate forms a cloudy precipitate in the medium when it reacts with the gelatin. Gelatinase activity is visible where clear zones in the cloudy precipitate are found, indicating the gelatin has been hydrolyzed.
What medium is used?
An example for Staphylococci might be Stone Gelatin Agar (also known as Staphylococcus Medium 110). But 3% gelatin can be added to other media to allow detection in other microbes.
How is the test performed?
An inoculum from a pure culture is streaked for isolation on an agar plate containing 3% gelatin. The streak plate is incubated at 35-37 C for 24 hours, at which time saturated ammonium sulfate is added to enable interpretation of results.
What reagents are added?
Ammonium Sulfate (saturated).
Performing this test in the VUMIE Online lab
To view the gelatinase test in VUMIE Online© Online Lab, complete the following steps:
1. Open the Tests link above the Virtual lab and select the Gelatinase Video.
2. Press the Play button to watch the video showing the test being performed.
3. Observe the results. If the bacterium possesses gelatinase, clear halos will surround the colonies of the microbe. A negative culture will not have clear halos.
4. Record the test result observed.