Who discover capsule in bacteria
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The capsule is found most commonly among gram-negative bacteria: Escherichia coli (in some strains) Neisseria meningitidis. Klebsiella pneumoniae.
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The capsule is found most commonly among gram-negative bacteria: Escherichia coli (in some strains) Neisseria meningitidis. Klebsiella pneumoniae.
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The cell capsule is a very large structure of some prokaryotic such as bacterial cells. It is a polysaccharide layer that lies outside the cell envelope of bacteria, and is thus deemed part of the outer envelope of a bacterial cell. It is a well-organized layer, not easily washed off, and it can be the cause of various diseases.
The capsule—which can be found in both gram negative bacteria and gram positive bacteria—should not be confused with the second lipid membrane (or bacterial outer membrane), which contains lipopolysaccharides and lipoproteins and is found only in Gram-negative bacteria. When the amorphous viscid secretion (that makes up the capsule) diffuses into the surrounding medium and remains as a loose undemarcated secretion, it is known as slime layer.
A bacterial capsule has a semi-ridged border that follows the contour of the cell. The capsule excludes India Ink when dyed. A slime layer is a non-ridged matrix that is easily deformed and is not able to exclude India Ink. Biofilms are composed of many cells and their outer barriers. The primary functions of both capsules and slime layers are for protection and adhesion.
Composition
It usually consists of polysaccharide
but can be composed of other materials (e.g., polypeptide(D-glutamic acid) in B.anthracis also peptidoglycan and muramic acid found in E.coli bacterial capsule. Because most capsules are so tightly packed, they are difficult to stain using standard stains because most stains cannot adhere to the capsule. For examination under the microscope, the bacteria and their background are stained darker than the capsule, which doesn't stain. When viewed, bacterial cells as well as the surface they are on, are stained dark, while the capsule remains pale or colorless and appears as a ring, or halo, around the cell.
Function
The capsule is considered a virulence factors because it enhances the ability of bacteria to cause disease (e.g. prevents phagocytosis). The capsule can protect cells from engulfment by eukaryotic cells, such as macrophages.
A capsule-specific antibody may be required for phagocytosis to occur. Capsules also contain water which protects the bacteria against desiccation. They also exclude bacterial viruses and most hydrophobic toxic materials such as detergents
Immunity to one capsule type does not result in immunity to the other types. Capsules also help cells adhere to surfaces
The capsule—which can be found in both gram negative bacteria and gram positive bacteria—should not be confused with the second lipid membrane (or bacterial outer membrane), which contains lipopolysaccharides and lipoproteins and is found only in Gram-negative bacteria. When the amorphous viscid secretion (that makes up the capsule) diffuses into the surrounding medium and remains as a loose undemarcated secretion, it is known as slime layer.
A bacterial capsule has a semi-ridged border that follows the contour of the cell. The capsule excludes India Ink when dyed. A slime layer is a non-ridged matrix that is easily deformed and is not able to exclude India Ink. Biofilms are composed of many cells and their outer barriers. The primary functions of both capsules and slime layers are for protection and adhesion.
Composition
It usually consists of polysaccharide
but can be composed of other materials (e.g., polypeptide(D-glutamic acid) in B.anthracis also peptidoglycan and muramic acid found in E.coli bacterial capsule. Because most capsules are so tightly packed, they are difficult to stain using standard stains because most stains cannot adhere to the capsule. For examination under the microscope, the bacteria and their background are stained darker than the capsule, which doesn't stain. When viewed, bacterial cells as well as the surface they are on, are stained dark, while the capsule remains pale or colorless and appears as a ring, or halo, around the cell.
Function
The capsule is considered a virulence factors because it enhances the ability of bacteria to cause disease (e.g. prevents phagocytosis). The capsule can protect cells from engulfment by eukaryotic cells, such as macrophages.
A capsule-specific antibody may be required for phagocytosis to occur. Capsules also contain water which protects the bacteria against desiccation. They also exclude bacterial viruses and most hydrophobic toxic materials such as detergents
Immunity to one capsule type does not result in immunity to the other types. Capsules also help cells adhere to surfaces
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