What reagents are used to develop the red color in the nitrate reduction test?

In the nitrate reduction test, the development of a red color indicates the presence of nitrites, which are produced when nitrates are reduced by certain bacteria. The specific reagents used to detect the nitrite in this reaction are sulfanilic acid and α-naphthylamine. When these reagents are added to a culture that has reduced nitrates to nitrites, they react with the nitrites to form a red azo dye, allowing for a clear visual indication of nitrate reduction.

This process is significant in microbiology because it helps differentiate among various bacterial species based on their metabolic capabilities related to nitrate. The efficient identification of these traits supports the classification of bacteria in clinical diagnostics and environmental microbiology.

Other options listed do not relate to the nitrate reduction test. For example, Ehrlich's and Kovac's reagents are used in different types of tests (such as for indole production), while o-Nitrophenyl-β-D-galactopyranoside is a substrate for testing enzyme activity related to galactosidases. Kovac's reagent is specific for detecting indole and not involved in the nitrate reduction process.