Microbiology: Phenylalanine Deaminase Test

The phenylalanine deaminase test is a biochemical test used to identify bacteria in the Enterobacteriaceae family, specifically the genera Proteus and Providencia. The test detects the enzyme phenylalanine deaminase, which converts phenylalanine into phenyl pyruvic acid. This acid reacts with ferric chloride, resulting in a green color change, indicating a positive result. A lack of color change indicates a negative result. The video explains the test's mechanism, detection method, and how to interpret results, concluding with a demonstration.

Which two genera within the Enterobacteriaceae family are identified using the phenylalanine deaminase test?

• Escherichia and Salmonella

• Proteus and Providencia

• Shigella and Yersinia

• Klebsiella and Enterobacter

What is the role of phenylalanine deaminase in the biochemical test?

• It converts phenylalanine into glucose.

• It converts phenylalanine into phenyl pyruvic acid.

• It converts phenylalanine into lactic acid.

• It converts phenylalanine into ammonia.

What is the purpose of adding ferric chloride in the phenylalanine deaminase test?

• To neutralize the solution

• To provide a nutrient source

• To react with phenyl pyruvic acid and indicate a color change

• To sterilize the test environment

What color change indicates a positive phenylalanine deaminase test result?

• Red

• Blue

• Green

• Yellow

In the practical demonstration, what does a lack of color change indicate?

• Presence of Escherichia coli

• Presence of phenylalanine deaminase

• Absence of phenylalanine deaminase

• Presence of Proteus or Providencia