Bacterial Endospore and Capsules

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Date Performed: Date Submitted: Exercise No. 9 Bacterial Endospores and Capsules Introduction: Endospores are possessed by bacteria such as Bacillus. By forming spores, bacteria can survive in extreme conditions. Spores are resistant to heat, UV radiation and chemicals because they are comprised of a tough proteinaceous covering called keratin. Bacteria can form endospores just hours after exposure to harsh conditions. The normally-growing cell that forms the endospore is called a vegetative cell. Spores are metabolically inactive and dehydrated. They can remain viable for thousands of years. When spores are exposed to favorable conditions, they can germinate back into a vegetative cell in just a few minutes. The cell envelope is a term used to describe the several layers that enclose the protoplasm of the cell. The cell cytoplasm is surrounded by the plasma membrane, a cell wall and a capsule. Outside the cell wall, may be a polysaccharide capsule or glycocalyx. The purpose of the capsule stain is to make the bacterial capsule visible. The water-soluble capsule of some bacterial cells is often difficult to see by standard simple staining procedures or after the Gram stain. Capsule staining methods were developed to visualize capsules and yield consistent and reliable results. Methodology: A. Bacterial Endospore A smear of B. subtilis was fixed into a slide. The slide was flooded with malachite green before passing over to the flame several times until it “steamed”. The stain was replenished as it was continued to pass over the flame without letting it to boil. After it was rinsed with tap water, safranin was added as a counterstain. It was rinsed and air-dried before it was examined under OIO. B. Bacterial Capsules A small drop of nigrosin was placed near the edge of a clean slide. A loopful of the culture was then mixed with nigrosin.
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