Micro305_Lab Report 1

Micro305_Lab Report 1 - Micro 305 February 14, 2007 Lab...

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Micro 305 February 14, 2007 Lab Report 1: Staining Introduction Simple Staining Simple staining is the simplest of the staining methods. The reason one stains is to increase the cells contrast so that they can be seen more easily by a microscope. Simple staining dyes the walls of the bacteria so that they are visible under the microscope. Most bacteria are negatively charged; therefore, a basic dye is used to attract to the bacteria. In this procedure, a student uses a basic dye called methylene blue to stain a strain of C. Diphtheriae to observe under the microscope. Gram Stain Gram staining is one of the most important staining procedures. The gram stain differentiates gram-positive bacteria from gram-negative bacteria. During this procedure the bacteria are stained twice in order to distinguish between the different types. The primary stain is crystal violet. Gram-positive bacteria have a thick layer of peptidoglycan in the cell wall, which holds the crystal violet. In this case, Gram’s iodine acts as a mordant. The iodine forms an insoluble complex with the crystal violet dye only in the gram-positive bacteria. Alcohol is added and decolorizes the gram-negative bacteria. Finally, safranin is added as a counter stain to give the gram-negative bacteria a red or pinkish color. In this lab, a student observes gram-positive bacteria, M. Luteus , and gram- negative bacteria, E. Coli , and a mixture of both. The purpose of this is to be able to distinguish between gram-negative and gram-positive bacteria after a Gram stain.
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Acid-Fast Stain Acid-fast staining is used with bacteria in the genera Mycobacterium and Nocardia . These bacteria have a unique material in their cells walls called mycolic acid.
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Micro305_Lab Report 1 - Micro 305 February 14, 2007 Lab...

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