The nitrate reduction test is an important biochemical test in microbiology. It is used to differentiate the various gram-negative rods and also mycobacteria.

Nitrate reduction test principle

Some anaerobic bacteria use nitrates in an anaerobic environment. As a result, they produce NITRITE and NITROGEN gas.

Nitrite changes the color of media, while nitrogen gas can be seen in the form of a bubble.

Nitrate reduction test reagents

  1. Nitrate Agar
    1. Peptone
    2. Agar
    3. Potassium Nitrate
    4. Distilled water
  2. Sulfanilic Acid
  3. Alpha Naphthylamin

How to perform nitrate reduction test

  1. First of all, inoculate the medium by streaking the slant and stabbing it to the butt with test organism culture.
  2. Incubate at 35 C for 4 hours.
  3. Add one drop of sulphanilic acid and one drop of naphthyl amine to the slant.
  4. Now for a change in color, if red color is seen, the result is positive otherwise negative.

Nitrate reduction test positive result

After incubation for 4 hours, add one drop of sulphanilic acid and 1 drop of naphthyl amine. If a red color appears on the medium, it will be considered a nitrate reduction test-positive result.

What does nitrate reduction test for

A nitrate reduction test was used to identify the anaerobic gram-negative rod. All Enterobacteriaceae reduce nitrate.

Nitrate reduction test control

Positive Control: E.coli was used as a positive control in the nitrate reduction test.

Negative Control: Streptococcus bacteria use as a negative control in the nitrate reduction test.

Reagent for nitrate reduction test?

The nitrate reduction test basically consists of 3 reagents. One is nitrate agar and the other two are.
1. Sulfanilic acid
2. Alpha Naphthylamine

Does e.coli reduce nitrate?

E.coli reduces nitrate into nitrite and nitrogen gas (N2).

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