The nitrate test was performed in order to indicate if our bacteria was able to reduce nitrate ions to nitrite ions or nitrogen gasses. Nitrate reduction is usually for energy production during anaerobic conditions. To determine whether the bacteria used nitrate reduction can test the presence of nitrite ions. To detect nitrite ions, sulfanilic acid and dimethyl alpha naphthylamine are added to bacteria inoculated in nitrate broth. If the broth turns pink, nitrite is present, and the results for nitrate reduction are positive. However, having no color change does not determine a negative result. Instead, Zinc has to be added to determine if the nitrate ions were reduced to molecular nitrogen. If the color does not change after the addition of Zinc, the results are considered to be negative.
First we inoculated a nitrate broth tube with our bacteria and let it incubate for 48 hours. Next, we added 5 drops of the two reagents listed above and proceeded to mix the contents. Right away, our broth turned red. Our bacteria is positive for nitrate reduction. We did not have to add zinc to the broth because the two reagents gave us instant results. The broth contained nitrite ions!
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