Final answer:
The essential amino acid tested for indole production in microorganisms is tryptophan. This test helps identify bacteria that can metabolize tryptophan, thus aiding in bacterial identification and diagnostics.
Step-by-step explanation:
Indole production is a test that is used to determine the ability of microorganisms to degrade the essential amino acid tryptophan. Among the given options, tryptophan is the correct answer as it is the amino acid that is tested for indole production through the metabolic pathway known as the tryptophanase pathway. This assay is a part of the standard biochemical testing of bacteria in microbiology.
Essential amino acids, such as tryptophan, cannot be synthesized by the body and must be obtained through the diet. The indole test is thus important in microbiological diagnostics to identify the metabolic capabilities of different microorganisms, such as distinguishing between different members of the Enterobacteriaceae family.
A positive indole test indicates that the organism can metabolize tryptophan to produce indole, pyruvate and ammonia. In clinical diagnostics, this can assist in the identification of bacteria that have pathogenic potential or in determining microbial composition in environmental samples.