Essay on A Report On The Urease Test

Essay on A Report On The Urease Test

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The Urease Test is used to differentiate organisms who are able to rapidly hydrolyze urea through the production of the enzyme urease. This test applies more to gram-positive cocci who are catalase-positive. Urease is critical in detoxification of waste products and supplies a source of nitrogen for amination reactions that produce amino acids and nucleotides (Department of Biological Sciences, 2015). The test was performed on a slant agar that has a high concentration of urea and contains a phenol red pH indicator. The test tube that contained the slant agar was inoculated and placed in aerobic incubation at 37°C for 48 hours. The phenol red pH indicator is the differential component which is yellow or orange when the pH is 8.4 or below, and red or pink when the pH is above 8.4. The medium was made to differentiate between rapid urease-positive bacteria and urease-negative bacteria. The medium also contained a potassium phosphate buffer which prevents the alkalinization of the medium from peptone metabolism (Atlas & Snyder, 2015). So in order for the hydrolysis of urea to occur, the bacteria must overcome the buffer. The hydrolysis of urea produces ammonia and raises the pH in the medium, which turns the slant pink.
The Nitrate Reduction and Denitrification test detects for the reduction of nitrate to nitrite by testing for the presence of nitrite. Anaerobic respiration involves the reduction of an inorganic molecule, like nitrate reduction, from the lack of oxygen. Many nitrifiers, bacterial species that contain the enzyme nitrate reductase that allows them to reduce nitrate to nitrite in one step (Slonczewski & Foster, 2015). Other bacteria are capable of further reducing nitrite into ammonia, nitrous oxide, or nitrogen thro...


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...ery strong and stable acids. The strong acids that are produced causes the pH to become very low. The mixed acid fermentation pathway produces acids such as acetic acid, lactic, succinic, and formic acid (Department of Biological Sciences, 2015). The medium used in this test is the same as the VP Test, which is MR-VP broth. Methyl red dye, a pH indicator, is added to the broth and only detects very strong acids. The color is red at a pH of 4.4 and yellow at a pH of 6.0. Organisms who do not use the mixed acid fermentation pathway, end up producing acids that are unstable, which end up being converted to more neutral end products and therefore changing the pH indicator to yellow. In order for the red color to be maintained, there must be large quantities of the strong and stable acid produced from the fermentation of glucose (Department of Biological Sciences, 2015).

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