Microbiology Unknown Paper.

1340 WordsJun 7, 20106 Pages
Lahela Correa 12/08/2009 Microbiology 140 Matthew Tuthill Unknown Lab Report Introduction There are many reasons for knowing the identity of microorganisms. The reasons range from knowing the causative agent of a disease in a patient, so as to know how it can be treated, to knowing the correct microorganism to be used for making certain foods or antibiotics. This study was done by applying all of the methods that I have been learned so far in the microbiology laboratory class for the identification of an unknown bacterium. The purpose of this lab was to identify two unknown bacteria cultures using various differential tests. The identification of these unknown cultures was accomplished by separating and differentiating possible…show more content…
Nitrate reduction was tested for by inoculating a nitrate broth with the unknown gram (-) culture, and allowing growth to take place. Adding 2 drops of both sulfanilic acid and α-napththylamine to the medium if the first test to see if nitrite is present. If nitrite is present, the medium turns red, indicating a positive test. However, if the medium does not change, a second test is performed to see if nitrite was further reduced. In this second test, zinc powder is added to the broth to catalyze the reduction of any nitrate present to nitrite. If nitrate is present when the zinc is added the reduction of this compound will cause the medium to turn red, from the previously added reagents. Red medium on the second addition indicates nitrate was not reduced and a negative test result. However, if the medium does not change after the addition of the zinc, the unknown is positive for nitrate reduction, as the nitrite has just been further reduced, preventing its detection. The result that yielded was positive on the first step. Triple Sugar Iron agar slant (TSI) was used to test for the fermentation of glucose and lactose, as well as the production of H2S. Gas production was also monitored, looking for fissures produced by production of gas during fermentation. The conversion of the originally red slant and butt of the agar to yellow indicates that
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