Changes

 

Many bacteria have a slimy layer surrounding them,which is usually ret'erred to as a capsule. The capsule's composition, as well as its thickness, varies with individual bacterial species. Polysaccharides, polypeptides, and glycoproteins have all been found in capsules. Often, a pathogenic bacterium with a thick capsule will be more virulent than a strain with little or no capsule since the capsule protects the bacterium against the phagocytic activity of the host's phagocytic cells. The capsule stain is of some importance in clinical microbiology (e.g., in the diagnosis of bacterial pneumonia and the fungus Cryptococcus neoformans). However, one cannot always determine if a capsule is present by simple staining procedures, such as using negative staining andIndia ink. An unstained area around a bacterial cell may be due to the separation of the cell from the surrounding stain upon drying. Two convenient procedures for determining the presence of a capsule are Anthony's capsule staining method and the Graham and Evans procedure.

Many bacteria have a slimy layer surrounding them,which is usually ret'erred to as a capsule. The capsule's composition, as well as its thickness, varies with individual bacterial species. Polysaccharides, polypeptides, and glycoproteins have all been found in capsules. Often, a pathogenic bacterium with a thick capsule will be more virulent than a strain with little or no capsule since the capsule protects the bacterium against the phagocytic activity of the host's phagocytic cells. The capsule stain is of some importance in clinical microbiology (e.g., in the diagnosis of bacterial pneumonia and the fungus Cryptococcus neoformans). However, one cannot always determine if a capsule is present by simple staining procedures, such as using negative staining andIndia ink. An unstained area around a bacterial cell may be due to the separation of the cell from the surrounding stain upon drying. Two convenient procedures for determining the presence of a capsule are Anthony's capsule staining method and the Graham and Evans procedure.