Overview
The capacity of the bacteria to reduce the nitrates by turning them into nitrites or into nitrogen is studied in this test, that is to say, the presence of nitrate reductase and nitrate reductase is analyzed.

The nitrate broth culture medium is used. To pinpoint the presence of nitrites in the culture medium two reagents are used: reagent A (0.8% sulfanilic acid in glacial acetic acid 5N) and reagent B (0.5% α- naphthylamine in glacial acetic acid 5N), which will be added after the incubation.

Carrying out the practical
The liquid culture medium is inoculated with a bacterial load of the strain under analysis using the inoculation loop.

nitrates – nitrates +

It is incubated at 37ºC for 24 hours and after incubation two drops of the reagents A and B of nitrates are added, which will highlight the presence of nitrites in the culture medium. If the nitrates have been reduced, the culture broth will turn a deep red color due to the presence of nitrites. If all the nitrate has been reduced to nitrogen, the presence of nitrites will not be revealed, but nitrogen bubbles will be observed, which are released in the test tube (similar to cava bubbles).

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