7. Edward wants to perform a nitrate test but he is confused about interpreting the results. Please explain to Edward how to perform the nitrate test and how to interpret each possible result.
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Nitrate reduction test can be used to differentiate between Pseudomonads and the Enterobacteriaceae. You inoculated your Nitrate broth with your unknown. After incubation, you added 5 drops of reagent A and 5 drops of reagent B. You observed a red color within 2 minutes. A. Is this a positive or negative reaction? B. Assuming you did not get a red color, you then added a pinch of Zinc powder to the tube. This time you did not get a red color. Is this a positive or a negative reaction? C. Explain your answers to questions A and B above. D. You streaked a starch plate with an organism. How would you know if the starch is hydrolyzed?
Madhur L.
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?
Adi S.
A microbiologist is testing several unknowns isolated from a soil sample for the ability to reduce nitrate. After incubating the organisms in nitrate broth and adding the appropriate test reagents and materials, the following results were determined. Analyze the observed test results summarized in the table below and match each interpretation of each result to the appropriate unknown. Unknown Observed Test Results A No Color Change After Adding Nitrate Test Reagents A and B and Zinc Powder; No gas in Durham Tube B Red Color After Adding Nitrate Test Reagents A and B; No gas in Durham Tube C Red Color After Adding Nitrate Test Reagents A and B and Zinc Powder; No gas in Durham Tube D No Color Change After Adding Nitrate Test Reagents A and B and Zinc Powder; Gas in Durham Tube E Red Color After Adding Nitrate Test Reagents A and B and Zinc Powder; Gas in Durham Tube 1 Reduced nitrate to nitrite 2 Reduced nitrate completely to nitrogen gas 3 Reduced nitrate to nitrite and then to ammonia 4 Could not reduce nitrate 5 Could not reduce nitrate but fermented sugars to carbon dioxide
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