Essay On Catalase Test

1163 Words 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
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It is also called differential staining because it differentiates among bacteria and can be used to distinguish between them based on the differences of cell wall structure. There are two major groups of bacteria, the gram positive staining cells and gram negative staining cells. In this procedure, the bacteria are first stained with crystal violet “basic stain”, and then treated with adding a mordant, iodine, which fixes the stain inside the cell. The stained cells are washed with a decolorizing agent, alcohol and then counterstained with …show more content…
Selective media favours the growth of some microorganisms and inhibit the growth of others. For example, MacConkey agar, which selects for gram negative bacteria which are able to ferment lactose, while the crystal violet in it inhibits the growth of gram positive cells. Differential media distinguish between different groups of microorganisms based on their biological characteristics. Such as, Mannitol agar which isolates and detects gram positive cells that ferments mannitol salt. Enriched media is a general purpose media supplemented by blood or other special nutrients, like blood agar that has also differential properties in respect to hemolysis (Victoria-Walz & Gilbride K,

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