The nitrate reductase test is a test to differentiate between

bacteria Bacteria (; : bacterium) are ubiquitous, mostly free-living organisms often consisting of one Cell (biology), biological cell. They constitute a large domain (biology), domain of Prokaryote, prokaryotic microorganisms. Typically a few micr ...

based on their ability or inability to reduce

nitrate Nitrate is a polyatomic ion with the chemical formula . salt (chemistry), Salts containing this ion are called nitrates. Nitrates are common components of fertilizers and explosives. Almost all inorganic nitrates are solubility, soluble in wa ...

(NO₃⁻) to

nitrite The nitrite polyatomic ion, ion has the chemical formula . Nitrite (mostly sodium nitrite) is widely used throughout chemical and pharmaceutical industries. The nitrite anion is a pervasive intermediate in the nitrogen cycle in nature. The name ...

(NO₂⁻) using

anaerobic respiration Anaerobic respiration is respiration using electron acceptors other than molecular oxygen (O2). Although oxygen is not the final electron acceptor, the process still uses a respiratory electron transport chain. In aerobic organisms undergoing ...

Procedure

Various assays for detecting nitrate reduction have been described.V.B.D. Skerman, A guide to the identification of the genera of bacteria, The Williams & Wilkins Co., Baltimore, MD, p.218 - 220 (1967). One method is performed as follows: #

Inoculate Inoculation is the act of implanting a pathogen or other microbe or virus into a person or other organism. It is a method of artificially inducing immunity against various infectious diseases. The term "inoculation" is also used more generally t ...

nitrate broth with an isolate and incubate for 48 hours. #Add two nitrate tablets to the sample. If the bacterium produces

nitrate reductase Nitrate reductases are molybdoenzymes that reduce nitrate () to nitrite (). This reaction is critical for the production of protein in most crop plants, as nitrate is the predominant source of nitrogen in fertilized soils. Types Euka ...

, the broth will turn a deep red within 5 minutes at this step. #If no color change is observed, then the result is inconclusive. Add a small amount of

zinc Zinc is a chemical element; it has symbol Zn and atomic number 30. It is a slightly brittle metal at room temperature and has a shiny-greyish appearance when oxidation is removed. It is the first element in group 12 (IIB) of the periodic tabl ...

to the broth. If the solution remains colorless, then both nitrate reductase and

nitrite reductase Nitrite reductase refers to any of several classes of enzymes that catalyze the reduction of nitrite. There are two classes of NIR's. A multi haem enzyme reduces NO2− to a variety of products. Copper containing enzymes carry out a single el ...

are present. If the solution turns red, nitrate reductase is not present.

References

Bacteriology Tests {{bacteria-stub