are bacterial stains charged
Assignment: Upon completion of the laboratory you should. 1  Be able to describe the procedure for heat fixation of a bacterial smear and discuss why fixation is necessary. 2  Define the following: acidic dye, basic dye, simple (direct) stain, negative (indirect) stain. 1 Use a toothpick to scrape material from your teeth near the gumline and stir this into the second drop of Congo Red. 2  Be sure to keep the two drops separate. 3  Air dry-DO NOT HEAT FIX. 4  Flood the slide with acid-alcohol (95% ethanol, 3% HCl) until it turns blue. They are used to examine structural differences between bacterial groups or to provide contrast to different structures within the same organism. Gram Stain. The Gram stain procedure uses 3 different stains. These are crystal violet, Gram's iodine, and safranin. Heat-fixing. Basic stains are applied to bacterial smears that have been heat-fixed. Heat-fixing kills the bacteria, makes them adhere to the slide, and coagulates cytoplasmic proteins to make them more visible. It also distorts the cells to some extent. 1. Begin with a heat-fixed emulsion 2. Cover the slide with crystal violet stain for 30 sec. Rinse 3. Cover the smear with iodine stain for 1 min. Rinse 4. Decolorize with ethanol by running it over the edge of the slide 3x. Immediately wash off with water 5. Simple Stain: A simple stain consists of a solution of a single dye. Some of the most commonly used dyes are methylene blue, basic fuchsin, and crystal violet. Simple stains allow one to distinguish the shape (morphology) of the bacteria. For example, E. coli and Bacillus Subtillus are bacilli or rod-shaped bacteria. In some cases, specific stains can be used to visualize certain structures (flagella, capsules, endospores, etc). of bacterial cells. There are several staining methods that are used routinely with bacteria. These methods may be classified as 1) simple (nonspecific) and 2) differential (specific). Wet Mount Preparation. 1. Place a loop-full of water on a clean glass side 2. Add bacteria to the drop. Don't over innoculate. Flame the loop after transfer 3. Gently lower a cover glass with your loop supporting one side over the drop of water. Negative Stain. In contrast to direct stains that bind to bacteria directly, a negative stain colors the background of a smear rather than the bacteria. These stains have negatively charged functional groups so they can't bind directly to negatively charged bacteria. The advantages of negative staining are: C. Gram Stain. 1  Transfer a loopful of the bacterial suspension to the surface of a clean glass slide, and spread it over a small area. 2  Flood the slide for one minute with a crystal violet solution. 3  Flood slide with Gram's iodine solution and allow to sit for one minute. 4  Flood slide with 95% alcohol and pour off immediately. 5  Flood the slide with ...
Yes