Question

Questions:

1. After adding Nitrate Reagent A and B, there was no red color change. You then added a pinch of zinc powder with a formation of a red color.

1. What category of nitrate reduction, would this microbe be?
2. Explain how this red color change occurred?
3. Denitrification part of the nitrogen cycle. Some microbes use this pathway anaerobically to convert nitrates (NO₃^- ) to nitrogen (N₂) gas. Other bacteria in anaerobic conditions, use what is called a Dissimilatory nitrate reduction to ammonium (DNRA) pathway to oxidize organic matter and use nitrate as an electron acceptor, reducing it to nitrite, then ammonium (NH₄⁺) See below for more information on DNRA

3. From a farmer’s point of view who has agricultural crops, would it be better for a nitrate reducing bacteria in the soil to be a denitrifier (denitrification) or a disassimilatory nitrate reducer to ammonium (DNRA) and why?

Answer 1

a. non -chemoorganoheterotrophic microbes

b. It is generally anaerobic respiration in which an organism uses oxygen from nitrate as an electron acceptor and reduce nitrate into intrite. if the organism is not capable of forming nitrite, after addition of zink powder catalyses the reaction to form nitrite and produce red color. Nitrite reacts with sulfanilic acid (reagent A) to form a nitrite-sulfanilic acid complex, then reacts with an α-naphthylamine (reagent B)  to give a red precipitate (prontosil), that is a water-soluble azo dye.