Using Selective And Differential Media Essay

1163 Words Dec 8th, 2015 5 Pages
The objective of these series of experiments was to identify two unknown bacteria’s. Broth culture #20 was selected and subjected to qualitative tests for identification. Gram stain tests were performed in order to identify which unknown is gram positive and gram negative. Using selective and differential media, like MacConkey agar which allows the growth of gram negative bacteria only that are able to ferment lactose. Also, mannitol agar was used which isolates and detects gram-positive bacteria. As well as blood agar, which is a nutritive media with differential properties in respect to hemolysis. The catalase test indicated catalase production and the coagulase test indicated a lack clotting in the tube. These tests were used for differentiation among gram positive. Furthermore, metabolism tests were used to differentiate among gram negative bacteria. For example, lysine decarboxylase test a color change from yellow to purple was indicated. The phenylalanine decarboxylase indicated the absence of phenylalanine deaminase. In methyl red test indicated a positive result while the Voges-Proskauer showed that the bacterium was not capable of performing a mixed acid fermentation. The indole test showed ability to hydrolyze tryptophan. The citrate test showed a negative indication of the bacterium ability to use citrate as a sole carbon source. The urease test showed no ability to urea hydrolysis. The conclusion drawn from these various tests was that the two unknown…

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