You have prepared a culture of an organism in a nitrate broth. There is no bubble in the Durham tube. There is red color change after adding the sulfanilic acid and naphthylamine reagents to the tube. What is your interpretation of the test?
Added by Iker A.
Step 1
Step 1: Observe the Durham tube — there is no bubble, so no detectable gas production in the broth (no obvious denitrification to N2/NO). Show more…
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Nitrate-Negative Species: Nitrate Reagent A (Sulfanilic Acid) Nitrate Reagent B (alpha-Naphthylamine) + Zn powder No change in color is observed when Nitrate Reagents A and B are added to the inoculated/incubated broths. A red color is observed as Nitrate Reagents A and B react with nitrite produced from nitrate by nitrate reductase. Nitrate-Positive Species: A red color is observed as Nitrate Reagents A and B react with nitrite produced from nitrate by nitrate reductase or No change in color is observed when Nitrate Reagents A and B are added because nitrite produced from nitrate has been further reduced. Nitrite (NO3) + Sulfanilic Acid (Nitrate Reagent A) + alpha-naphthylamine (Nitrate Reagent B) Nitrite (NO2) + Zn dust Nitric Oxide (NO) Nitrous Oxide (N2O) or Nitrogen (N2)
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A Nitrate broth was inoculated with the bacteria isolated from the keyboard, and the broth was incubated. After incubation, chemicals were added to the culture tube according to the standard protocol. The results are shown below. Which of the following is correct, based on the outcome of the Nitrate Reduction test? Nitrate broth culture after the addition of Nitrate Reagents A and B Nitrate broth culture after zinc was added The bacteria reduce nitrate. The bacteria reduce nitrite. The Nitrate Reduction test is positive. The Nitrate Reduction test is negative.
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One of the more involved tests from this lab is the Nitrate reduction test. Answer the following questions about the nitrate test: - What nitrogen-containing compound is in the uninoculated media? - Sulfanilic acid and Napthalamine acetate are added to the media after incubation. What nitrogen-containing compound do these reagents test for? How is this visualized? - If Sulfanilic acid and Napthalamine acetate do not produce a color change, what can be interpreted? - To which tubes should zinc be added? - If there is a color change after zinc is added, what can be interpreted? - If there is no color change after zinc is added, what can be interpreted?
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