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 interpretation of results, concluding with a demonstration.

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

• Shigella and Yersinia

• Klebsiella and Enterobacter

• Proteus and Providencia

• Escherichia and Salmonella

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

• It oxidizes phenyl pyruvic acid into phenylalanine.

• It converts phenylalanine into phenyl pyruvic acid.

• It reacts with ferric chloride to produce a green color.

• It breaks down ammonia into phenylalanine.

How is the presence of phenyl pyruvic acid detected in the phenylalanine deaminase test?

• By adding ammonia

• By using a pH indicator

• By adding ferric chloride

• By heating the sample

What does a green color change indicate in the phenylalanine deaminase test?

• Absence of phenylalanine deaminase

• Presence of Proteus or Providencia

• Presence of Escherichia

• Presence of Klebsiella

What does no color change signify in the phenylalanine deaminase test?

• A negative result for phenylalanine deaminase

• A positive result for Providencia

• A positive result for Proteus

• Presence of phenyl pyruvic acid