The first test performed to identify the unknown was gram-staining. This showed whether the microbe was violet or pink. Violet shows if it is positive since it has a thicker layer of peptidoglycan in the cell wall and pink for Gram-negative because it has a thinner layer of peptidoglycan in the cell wall. The results for the unknown were violet, which means it is a gam-positive allowing all of the gram negatives to be ruled out. This test also allowed the shape of the microbe to be determined, which is cocci in tetrads. However, the grouping of the cocci is not very reliable because some could become pushed together. The next test that was performed in order to narrow down the microbes was the streak plate method on trypticase soy agar(TSA)…show more content… To narrow down the unknown even further mannitol salt agar was used to determine if the microbe was salt tolerant and/or ferment mannitol. The color of the agar starts out as red but changes to yellow if the microbe can ferment mannitol. The microbe can also grow on the agar even if it does not ferment mannitol because it can also be salt tolerant. Therefore, if it ferments mannitol it is salt tolerant. The results for the unknown were that it is salt tolerant because it was able to grow on the plate but cannot ferment mannitol because the color of the plate remained red. This allowed the unknown to be identified as M. luteus, because it is gram-positive, salt tolerant and does not ferment mannitol. However, three more tests were performed in order to verify the identification. One of the tests used for verification was the catalase test, which test for the presence of the catalase enzyme. The results came back as positive because of the bubbles resulting from the reaction of the catalase enzyme and hydrogen peroxide. This test only verified that the unknown was not Enterococcus faecalis, because the other three organisms all had positive results from the
