2 Flashcards
thread-like appendages composed entirely of protein, 12–30 nm in diameter.
Bacterial flagella
is a whip-like filament, long, thin, helical structure composed of protein flagellin.
Flagella
Three types of Flagella arrangement are known:
(1) Monotrichous (single polar flagellum).
(2) Amphitrichous (flagella @ both ends).
(3) Lophotrichous (cluster at one end).
(4) Peritrichous (flagella covering the cell).
(5) Atichous (with no flagella).
Bacterial flagella are composed of three parts:
a- Filament
b- Hook
c- Basal body
Flagella function:
a- Rotation propels bacterium through environment.
b- The movement of bacterium toward or away from a particular stimulus is called taxis.
• Guide bacteria in a direction in response to external
environment stimulus:
1) chemical stimuli – chemotaxis; positive and negative
2) light stimuli – phototaxis
rod like, protein extensions, these projections adhere to one another and to substances in the environment or to their host
Fimbriae
Some fimbriae carry
enzymes that render soluble, toxic ions into insoluble, nontoxic form.
Fimbriae function
a- Sticky, bristle-like projections.
b- Used by bacteria to adhere to one another and to substances in environment.
c- Used by bacteria to move across a surface.
d- Save an important function in biofilm.
is a type of fimbria,
longer than fimbria but shorter than flagella.
Typically only one to a few pili are present per cell.
Pili
How are pili different from bacterial flagella?
Bacterial flagella are flexible structures that rotate to propel (push) the cell,
pili are hollow tubes used to transfer DNA from one cell to another.
Function of bacterial cell wall:
1- Provide structure and shape and protect cell from osmotic force.
2- Assist some cells in attaching to other cells or in resisting antimicrobial drugs. 3- They provide ligands for adherence
4- Have receptor sites for drugs or viruses.
5- Composed of peptidoglycan (polysaccharide).
6- In addition, bacterial cell wall fragments can have immune stimulatory and cytotoxic properties and thus play important roles in pathogenesis and disease.
Scientists describe two basic types of bacterial cell wall;
Gram-positive &
Gram- negative
Gram-positive bacterial cell wall:
1- Relatively thick layer of peptidoglycan.
2- Contain unique polyalcohols called teichoic acid.
3- Appear purple following Gram staining procedure.
4- Presence of up to 60% mycolic acid in acid-fast bacteria (T.B)
Gram-negative bacterial cell wall:
1- Have only a thin layer of peptidoglycan.
2- Bilayer membrane outside the peptidoglycan contain phospholipids, proteins, and lipopolysaccharide (LPS)
3- Appear pink following Gram staining procedure.