Protien-Indole (tryptophan), Citrate, Nitrate, and Urea Tests.

Uninoculated tubes:

Above (left to right) citrate tube, indole tube, nitrite tube, and urea tube

The Citrate test determines whether a bacterium can utilize citrate as its sole source of carbon and energy. If our bacteria does, it has the enzyme, citrate permease and will turn the green agar blue. Our bacteria turned slightly turned the agar blue, therefore, our bacteria does utilize citrate.

The indole test determines the ability of some bacteria to split the amino acid tryptophan into indole and pyruvic acid. If the bacteria produces indole, a red layer would form at the top of the test tube. Our bacteria did not produce a red layer, therefore, this test is negative. Our bacteria does not use the amino acid, tryptophan.

The nitrite test determines if a bacterium is able to reduce nitrate ions to either nitrite ions or to nitrogen gas. Our sample did not turn red upon adding the zinc, therefore our bacteria is positive and is capable of reducing nitrate ions.

Finally, the urea test allows us to determine whether a bacteria has the ability to hydrolyze urea. We inoculated our bacteria into the urea-containing broth and if the tube turned bright pink, the bacteria would test positive, showing that it has the enzyme urease. Our bacteria did not turn pink but remained the same color. So, our bacteria does not have urease and therefore it cannot hydrolyze bacteria.

During the second part of lab, we prepared a petri dish of our bacteria and then placed seven different antibiotic tablets in the plate: Penicillin, vancomycin, novabiocin, tetracydine, erythromycan, chloramphenicol, and neomycin. We will find out next lab whether our bacteria are sensitive to the antibiotics...