Week 8

For week 8, we performed several tests to determine the enzymatic properties of our bacteria. These tests included Methyl Red test (mixed fermentation), Citrate utilization test, Indole (tryptophan degradation) test, Oxidase test, Nitrate Reduction Test, and the Urea hydrolysis test.
To begin, we inoculated test tubes containing the medium of each specific test, and then incubated them until the following lab to determine the results.

The following lab period, upon retrieving our test tubes, we determined that our bacteria had a negative test with Urea, Oxidase, and Citrate, but a positive test with Nitrate, Indole, and the methyl red fermentation test.

 
For the Nitrate test, we took our inoculated nitrate broth tube, and added 5 drops of nitrate reagent A (sulfanilic acid) and 5 drops of nitrate reagent B (dimethyl-alpha-naphthylamine). Our nitrate broth immediately took on a deep red color, indicating a positive test.

For our Indole test, we took our inoculated tryptone broth tube and added 10 drops of Kovac's reagent. A red layer appeared at the tope of the tube, indicating that the test was positive.

Next, we took our methyl red broth tube and poured out half into another sterile test tube for a second fermentation test (Voges-Proskauer Test) We then added 5 drops of methyl red (pH indicator) to the first tube.

Our tube took on a reddish color, indicating a positive test.

We then took the second test tube of methyl-red broth and added 15 drops of Baritt's reagent A (alpha-naphthol) and 5 drops of Barritt's reagent B (KOH) to the tube. Our broth did not change colors, indicating a negative test.
Finally, we performed the oxidase test. Taking our inoculated broth tube for the test, we took a sample using a sterile swab. We then added the oxidase reagent to the swab. There was no change in color, indicating a negative test for oxidase.

In conclusion, through these tests, we concluded that our bacteria:
a) is able to ferment glucose via mixed-acid fermentation, but not through butanediol fermentation (methyl red)
b) does not use citrate as its sole source of carbon and energy (Citrate test)
c) has the ability to split the amino acid tryptophan into indole and pyretic acid (Indole test)
d) does not have cytochrome oxidase (oxidase test)
e) is able to reduce nitrate ions to either nitrite or to nitrogen gas (nitrate test)
f) and is unable to hydrolyze urea