Cellular Structures and Pathogenicity

Pathogenicity is the ability to produce a disease. Although bacteria cells have many different internal as well as external structures, three important structures are going to be mentioned such as the flagella, capsule, and slime layer. These structure are important because their are several microbial pathogens that cause disease and infection.

The flagella is a long thin helical appendage of cells that provides a means of locomotion or movement. Most flagella rotate like twirling L-shaped hooks. An example would be a dough hook used on a kitchen mixer or rotating like the string on a weedwacker. Motion occurs as the energy is used to make one of the rings in the cell membrane rotate with the other.

The capsule is another external structure important to the cell. It is a protective structure outside the cell wall of the organism that secretes it. Capsules typically consist of complex polysaccharide molecules arranged in a loose gel. The chemical make up of the cell is unique to the strain of bacteria that secreted it. If bacteria cells lose their capsules they are less likely to cause disease and are more likely to be destructed.

The slime layer is another external structure. A slime layer is less tightly bound to the cell wall and is usually thinner that a capsule. When the slime layer is present its function is to protect the cell against drying out. It helps to trap nutrients near the cell and sometimes it is able to bind cells together. The slime layer is what attracts the bacteria to adhere to any objects that may be in their environment. The environments may be rock surfaces or roots of plants. This is so that they can stay at areas where there are a lot of sources of nutrients and oxygen. This slime protects bacteria on the bottom layers from environmental or man-made chemicals. Oral bacteria stick in the slime layer and form plaque. The slime layer keeps the bacteria in close proximity to the tooth surface which is the cause of tooth caries. Plaque is tightly bound to the tooth surface, and should be removed by daily brushing (Black, 2008). Glycocalyx is the glycoprotein-polysaccharide covering that surrounds many cells. A glycocalyx is considered a slime layer is when