In searching for the identity of our unknown soil microorganism, we performed an experiment to determine whether nitrate may be reduced by our microbe. Nitrate reductase controls the reduction of nitrate to nitrite and indicates that nitrate could be used as an electron acceptor during anaerobic respiration. The experiment determines whether a microbe produces nitrogen gas, reduces nitrate to nitrite, or will reduce nitrate to another form other than nitrite. If an organism releases nitrogen gas, then bubbles will become visible at the top of the medium, as seen in the positive control. If an organism does not produce bubbles, then a solution of sulfanilic acid and alpha-naphthylamine is added to the incubated medium. Whether the medium turns red in color determines if nitrate reduces to nitrite.
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| Positive Control |
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| Negative Control |
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| Unknown |
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| Blank |
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| Unknown compared to Negative control |
Our unknown produced the same results as our negative control, indicating that it reduces nitrate to nitrite. Bacteria reduces nitrate for various reasons. Nitrate may be used as a source of nitrogen for cellular growth, a terminal electron acceptor in creating metabolic energy, or ridding the organism of excess reducing power in redox balancing.
Following the dichotomous key, it appears that due to our microbes ability to reduce nitrate, our bacteria would be Actinomyces spp. Further testing must be completed in order to confirm.
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