Lab Report: Gram Negative Unknown Bacteria

MICROBIOLOGY 3444-007

Gram Negative Unknown

Unknown Bacteria #14

LeNaiya Kydd

4/2/2014

Abstract
In order to be able to identify the unknown organism that was given to us, we had to conduct a number of different tests. These biological tests are used because they help us be able to identify the properties of the unknown we have and be able to compare our observed results with actual results of all the potential organisms. When all of the data of the test are put together it is easy to figure out the identity of the unknown. Each test is briefly introduced, what it is and what it tests for. The way each test is conducted needs to be correct so the results will be accurate, and when doing these tests it is important to use aseptic
The inoculating loop was sterilized in the flame before and after being put into the TSA slant containing the unknown bacteria. After the medium was inoculated it was incubated in the 37ºC room for 24 hours. When that was finished the test tube was taken out and 15 drops of methyl red indicator was to the medium(Leboffe & Pierce, 162).
Voges-Proskaur Test
The next test was the VP test. As always the inoculating tool was sterilized in the flame of the burner before and after picking up the bacteria. After the media was inoculated it was kept in the 37ºC room for three days, in order to give accurate results. I then took out the test tube and vortexed it to mix the medium. The last step was to added 15 drops of Barritt’s reagent A and 5 drops of Barritt’s reagent B to the tube(Leboffe & Pierce, 162).
Citrate Test
The first step of the Citrate test was to inoculate the media with the bacteria from the TSA slant. Again the inoculating loop was sterilized before and after the test with the burner. The test tube was kept for 24 hours in the 37ºC room(Leboffe & Pierce, 176).
Urea
This means that the unknown can have the citrate permease enzyme, which permits it to utilize citrate as the only carbon source. The change in the color of the media is due to the Bromthymol blue dye present in the media, which makes it green at pH 6.9 and blue at pH 7.6 and up. So there was an obvious increase in the pH of the media(Leboffe & Pierce, 176).
Urea Test
After 6 days of incubation the urea broth of the Urea test finally turned bright pink indicating the bacteria positive for the production of urease, the enzyme that hydrolyzes urea into ammonia and carbon dioxide. The presence of urease in the broth causes the pH of the media to increase, which is why we can observe the color change from orange to pink(Leboffe & Pierce, 188).
Gelatin Test
After being in the 37º C room for 8 days the gelatin media from the Gelatin test was placed in the 4º C room for an hour to chill. If the media turned solid it was negative for gelatinase, if it was still liquid it was positive for the enzyme. With the unknown I had, the results were negative, meaning that the media was solidified. There was no production of gelatinase, the metabolic digestive enzyme that hydrolyzes gelatin(Leboffe & Pierce,