what is the metabolic reaction involved during the nitrate r

what is the metabolic reaction involved during the nitrate reduction test

Solution

Nitrate reduction test is used to differentiate organisms that posses nitrate reductase enzyme which converts nitrate to nitrite which are then degraded to different nitrogenous compounds in the cells.

The reagents used to check for nitrate reductase enzyme are sulfanilic acid reagent and - naphthylamine.

Nitrate reducers will convert the nitrite to nitrous acid inside their cells. This nitrous acid reacts with sulphanilic acid to produce  diazotized sulfanilic acid which produces a red compound after reacting with - naphthylamine. The turning of the medium to red is a positive test.

When the medium does not turn red, The next step is to add zinc powder to the medium, which will then turn the unreduced nitrate and nitrite to red colored compound. This indicates a negative test.