What is/are similar between Methyl red and Voges Proskauer test? A) Both tests use the same medium B) Both tests determine the products of glucose fermentation C) Both tests use methyl red as pH indicator A and C A and B
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A) Both tests use the same medium B) Both tests determine the products of glucose fermentation C) Both tests use methyl red as pH indicator Show more…
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Methyl Red: This test determines the presence of acidic byproducts of glucose fermentation, specifically mixed acid fermentation. The test organism is inoculated into a tube of MRVP broth (Methyl Red, Voges-Proskauer broth), allowed to grow, and then tested for pH below 4.4 by adding the pH indicator Methyl Red. A bright red color indicates a positive result (pH below 4.4), whereas a negative result shows yellow (pH above 4.4). Voges-Proskauer: This test determines the ability of bacteria to produce acidic byproducts from glucose, specifically the presence of acetoin, an intermediate of 2,3 butanedio fermentation. The test organism is inoculated into a tube of MRVP broth, allowed to grow, and then tested for the presence of acetoin by adding 10 drops each of alpha naphthol and 40% KOH. A dull brick red color indicates a positive result. This result may require vigorous agitation and application of heat (placing the tube in the incubator) and may take up to 1 hour to develop. No change in the color of the tube indicates a negative result.
Dominador T.
Review Questions 1. Although Methyl Red Test and Voges-Proskauer Test uses the same medium (MR-VP broth) E.coli and E. aerogenes is giving different colors in each test (see the figure below). Please explain the reason. Escherichia coli Enterobacter aerogenes Methyl Red VP Methyl Red VP 2. In the citrate utilization test, indicator bromothymol blue (reactions given below) is used. Degradation of citrate is yielding formation of CO2. Which color do you expect to observe for a positive citrate test result?
Sri K.
In the previous lab we used another red pH indicator, phenol red. Compare the colors of phenol red and methyl red at neutral and acidic conditions. What is the difference between a selective medium and a differential medium? Explain why Levine EMB is considered a selective medium but Luisetti's is not. Use + or - to fill in this chart on the differences between E. coli and Enterobacter aerogenes. Organism Indole Methyl Red Voges Proskauer Citrate E. coli Enterobacter aerogenes
Madhur L.
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