Microbiology: Indole Test (Tryptophanase)

The video tutorial explains the indole test, a method used to identify gram-negative bacilli. It details the role of tryptophan and the enzyme tryptophanase in producing indole, which reacts with Kovacs reagent to produce a red color, indicating a positive result. The absence of this color suggests a negative result, meaning tryptophanase is not expressed. The tutorial provides a clear explanation of how to interpret the test results, emphasizing the simplicity and straightforward nature of the indole test.

What does a negative indole test result indicate about the expression of tryptophanase in bacteria?

Describe the appearance of the indole test results when the test is positive.