Definition for Nitrate reduction test
From Biology Forums Dictionary
Bacterial species may be classified into different groups depends on their ability to reduce nitrate to nitrite or nitrogenous gases provided in the growth medium. The reduction in nitrate can be coupled to anaerobic respiration in some bacterial species. Nitrate, present in the broth, is reduced to nitrite which is then reduced to nitric oxide, nitrous oxide, or nitrogen. The basis of nitrate reduction test the detection of nitrite and its ability to form a red colored compound when it reacts with reagent A which is sulfanilic acid and to form a complex (nitrite-sulfanilic acid) which then reacts with Reagent B which is α-naphthylamine to give a red precipitate (prontosil). Zinc powder act as a catalyst and that will favours the reduction of nitrate to nitrite. Nitrate reaction occurs only under anaerobic conditions. The medium is then transferred in tubes to make a low surface area to depth ratio that will limit the diffusion of oxygen into the growth medium. Most bacteria utilize the available oxygen in the medium for their growth and will rapidly produce anaerobic conditions for the further reactions.
