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