Appendages: Cell Extensions
- Appendages: structures that are outside the surface of bacteria.
- Flagella (Bacteria Propellers)
- Flagellum: appendage that offers mobility, self-propulsion, to swim freely in an aqueous habitat.
- Bacteria flagellum consists of 3 parts:
- 1. Filament
- Helical structure composed of proteins.
- Size: 20nm in diameter, 1-70nm in length.
- 2. Hook (Sheath)
- Filament inserted through curved, tubular hook.
- The hook is anchored by the basal body.
- 3. Basal Body
- Stack of protein rings that anchors the flagella through the cell wall to the cell membrane.
- Structure allows for 360 degree to propel in a direct foward movement.
- Types of Arrangement
- Monotrichous: single flagellum.
- Lophotrichous: small bunches of flagella emerging from the same site.
- Amphitrichous: flagella coming from both poles of the cell.
- Peritricous: flagella is dispersed randomly over the surface of the cell.
- Functions
- Chemotaxis: detect and move in response to chemical signals.
- Run: smooth linear direction toward a stimulus.
- Tumble: reversal of direction and stops to change course.
- Phototaxis: type of movement in response to light rather than chemicals.
- Periplasmic Flagella: Internal Flagella
- Spirochetes: corkscrew-shaped bacteria.
- Spirochetes have a mode of transportation caused by two or more long, coiled threads called the periplasmic flagella or axial filaments.
- Periplasmic flagella:
- Pilus & Fimbria
- Appendages that provide some form of adhesion, but not locomotion.
- Fimbria are refereed to as shorter, numerous strands.
- Stick to each other and surfaces.
- Can lead to biofilms and other aggregates on the surface of liquid.
- Or colonization on inanimate objects.
- Also can colonize and infect host because of tight adhesion between with fimbriae and and epithelial cells.
- Pili are refereed to as longer, sparser appendages.
- Elongated, rigid tubular structure made of pilin.
- Found only in Gram negative bacteria.
- Conjugation: partial transfer of DNA from one cell to another.
- Takes place only with compatible gram negative cells.