Theories of Staining Techniques
Staining bacteria with different dyes via staining techniques, allows in distinguishing the microorganism from its backgrounds. Also, helps in studying different internal structures such as vacuoles, cell walls and spores in details (Seeley and others 1991). Some staining techniques such as Gram staining, endospore stain and capsule stain are some of the theories of stains used in bacteriology today. Also, these staining procedures help in determining properties of an unknown culture.
Gram staining is a differential stain that helps in distinguishing between types of bacteria and it is the most useful staining procedure used today (Seeley and others 1991). In this kind of staining procedure, a basic dye, a mordant, a decolorizing agent and a counterstain is needed. First, prepare smears of an unknown culture, then spread a drop of the culture on a slide and let it air dry. After air drying, heat fix this slide by passing the slide three times through a bunsen flame. This allows the cells to adhere to the slide. Following the heat fixation, stain the slide with crystal violet, a basic dye for 30 seconds and then rinse with water. After rinsing off the crystal violet stain with water, apply iodine for 30 seconds. This act as a mordant that helps adhere the dye on the cell. After that, rinse with water and then decolorize with alcohol for 10-20 seconds. After decolorization, rinse again with water and add safranin for 20-30 seconds, acting as a counterstain. Then, rinse the stain out with water and blot off excess water. Examine this slide under oil-immersion objective and make drawings of your observations. After examining the slide under oil-immersion objective, the unknown bacterial culture had a thin wall and stained red/pinkish color with rod shape. This means that the bacterial was a gram negative and the cell walls have a “thin layer of peptidoglycan with outer layers of protein and lipopolysaccharides” (Seeley and...
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