What is the purpose of the test? This test determines whether the microbe produces the enzyme phenylalanine deaminase , which is needed for it to use the amino acid phenylalanine as a carbon and energy source for growth.
How is presence of phenylalanine deaminase determined? If phenylalanine deaminase is present, a degradation product is produced from phenylalanine. The product combines with iron compounds in an acidic environment to produce a green color.
What medium is used? The medium used is phenylalanine agar, a nutrient medium enriched with 0.2% phenylalanine . It is allowed to solidify at a slant.
How is the test performed? An inoculum from a pure culture is transferred aseptically to a sterile tube of phenylalanine agar to streak the slant. The butt of the tube need not be stabbed. The inoculated tube is incubated at 35-37 C for 24 hours. Then, reagents must be added to allow results to be determined.
What reagents are added? After incubation, five drops of 10% ferric chloride and five drops of 0.1N HCl are added and the tube is gently shaken. A positive result is indicated if a green color develops within five minutes.
To perform this test in VUMIE Online© Online Lab , complete the following steps:
Inoculation of Medium
1. Select the phenylalanine agar slant medium.
2. Complete the process of a tube-to-tube aseptic transfer to inoculate the medium by streaking the slant. Forgotten how to do these things? Watch the "Show Me How To" videos.
Incubation of the Inoculated Medium
3. Place the inoculated tube into the 35-37 C incubator.
4. Press the New Day button to move forward 24 hours. Forgotten how to do these things? Watch the "Show Me How To" videos.
Addition of Reagents
5. Incubate this test for only 24 hours.
6. Retrieve the incubated culture from the incubator.
7. This is a test that requires addition of reagents to bring about the change in appearance of a positive test.
Select the dropper tool and the appropriate reagent needed from the chemical shelf. Remove the cap lid. For this test, select 10% ferric chloride, add it, and then add 0.1N HCl.
Determination of Test Results
8 . Observe test result. For this test, the reagent turns the liquid below the slant green when giving positive results. If negative, no color change is observed.
9. Record test result.