IMViC Tests : Indole, Methyl Red, Voges-Prokauer, and Citrate Utilization {Lab 8 - May 21, 2015}

     For today's lab, we looked over the test tubes we had inoculated  during the previous lab and completed the tests and recorded the results. 

Madeleine gathering all
the different test tubes

Indole Test

      For the Indole test, we tested the ability of our unknown to split the amino acid tryptophan into indole and pyruvic acid. A tryptone broth tube was inoculated with our unknown bacteria and then incubated it. After incubation, we added five drops of Kovac's reagent to the culture. Ours resulted in the appearance of a red layer at the top, which was indicative of a positive test for the presence of indole.

Positive Indole Test

Methyl Red Test

     The methyl red test was done next. This test was done to determine the ability of some bacteria to ferment glucose via mixed acid fermentation. We inoculated our unknown into the methyl red/ voges-prokauer broth tube using aseptic techniques. The tube was then incubated. After incubation, we added 5-6 drops of methyl red to the tube. Our tube turned a red color indicating that we had a positive test for the mixed-acid fermentation pathway. 

Positive Methyl Red Test

Voges-Prokauer Test

     The Voges-Prokauer test was done to determine if our unknown had the ability to ferment glucose via butanediol fermentation.We took some of the broth from the methyl-red test (which had been inoculated and incubated; before we had added the methyl red) and placed it in a separate test tube. We added 15 drops of Barritt's reagent A and 5 drops of Barritt's reagent B to the tube. The tube was then shaken vigorously so that the oxygen from the air could aerate the medium. After 30 minutes, our tube remained yellow indicating a negative test. Our bacteria did not use butanediol as a fermentation pathway. 

Negative Voges-Prokauer Test

Citrate Test

     The citrate test would determine if our bacteria could use citrate as its sole source of carbon and energy. We inoculated our unknown onto a Simmmons citrate agar slant tube and incubated it. After incubation, the results were negative. If it had been positive, the slant would have changed to blue were the bacteria was; however, ours remained green.

Negative Citrate Test

Results/application:

IMViC tests are employed in the identification/differentation of members of family enterobacteriaceae. With these tests, one can determine whether a certain bacteria is part of the family enterobacteriaceae and further identify it if it is.