Other Tests {Lab 8 - May 21, 2015}

     We completed some of the last remaining tests on our unknown. These tests included: Phenylalanine Deamination Test, Triple Sugar Iron Test, Urea Hydrolysis Test, Litmus Milk Reactions, and Coagulase Test. 

Phenylalanine Deamination Test

     This test was performed to determine the ability of our bacteria to remove the amino group from the amino acid phenylalanine. To perform this experiment we need a phenylalanine agar slant tube, 10% FeCl3 solution, and our Unknown. We transferred our unknown to the phenylalanine agar slant using aseptic techniques, then incubated it for 24 hrs. After incubation, we added around 5 drops of 10% FeCl3 to the tube. A positive test would result in a green color; a negative test would result in no color change or a reddish color. Ours turned green meaning our bacteria was able to remove the amino acid.

Triple Sugar Iron Test

      This test differentiates among the gram-negative enteric bacilli as to their ability to ferment glucose, lactose, and sucrose and to produce H2S. We needed: triple sugar iron agar slant tube and  our unknown bacteria. After inoculation of our bacteria, we incubated it for 24 hrs. We checked for color changes, appearances of gas, and black precipitate. Ours was yellow colored indicating acid and had gas in it.

Urea Hydrolysis Test

    This test was conducted in order to determine if our bacteria had the ability to hydrolyze urea. We needed a urea containing broth and our unknown bacteria. 

Ashley and Elisabeth holding
the Urea Broth

      Using aseptic techniques, we inoculated our unknown in the urea broth. This was then incubated for 24 hrs. Afterwards, we observed the tube looking for any color changes. There was no change in the color of the urea which signified that ours was a negative test and it did not hydrolyze urea. 

Litmus Milk Reaction

      For this test, we could differentiate among bacteria by their ability to utilize lactose, protein, and litmus in litmus milk. We needed our unknown and a litmus milk tube. We used aseptic technique to transfer our unknown into the litmus milk tube; we then incubated  the tube. After 24 hrs it was already reacting with the litmus milk forming small white curdles at the bottom of the tube. After 7 days, the entire tube was curdled. Our bacteria can ferment lactose.

Our litmus milk after 24 hrs

Our litmus milk after 7 days

Gelatin Test

     This test was done to determine the ability of our bacteria to hydrolyze gelatin. We needed a nutrient gelatin agar deep tube and our bacteria. After inoculation, we incubated our bacteria for 48 hrs. Afterwards, we placed our tube in a refrigerator for 15 minutes. After 15 minutes, the gelatin in our tube was a solid. We placed the test tube back in the incubator over night, and placed it in the refrigerator once again. After 15 minutes, the gelatin was once more a solid. Therefore, our bacteria could not hydrolyze gelatin.

Gelatin, solid
(negative gelatin hydrolysis)