Basic structure of prokaryotes
Color and Size
Cell envelope
is the structure that surrounds the cytoplasm of bacteria
•LIPOPOLYSACCHARIDE –
LPS of outer membrane of Gram –ve is Endotoxin –Produce hypotension, fever, shock –Three components
•Lipid A is toxic component
•Core polysaccharide of 5 sugars
•Outer polysaccharide of up to 25 sugar- O somatic Ag
LPS of outer membrane of Gram –ve is Endotoxin –Produce hypotension, fever, shock –Three components
•Lipid A is toxic component
•Core polysaccharide of 5 sugars
•Outer polysaccharide of up to 25 sugar- O somatic Ag
Gram positive
•Cytoplasmic membrane
•Thick peptidoglycan layer (Cell wall)
•Thick peptidoglycan layer (Cell wall)
Gram negative
•Cytoplasmic membrane(Also called Inner membrane)
•Thin peptidoglycan layer
•Outer membrane
•Thin peptidoglycan layer
•Outer membrane
CELL ENVELOPE IN GRAM +ve AND GRAM –ve BACTERIA
BACTERIAL CELL STRUCTURE
•Capsule –Layer covering entire bacterium
–Polysaccharide except Bacillus anthracis-polypeptide capsule
–Determine serotype e.g. Strep pneumoniae 84 serotypes
–Virulence factor : Negative charge resist phagocytosis. Bacteria that lose capsule-become avirulent
–Polysaccharide except Bacillus anthracis-polypeptide capsule
–Determine serotype e.g. Strep pneumoniae 84 serotypes
–Virulence factor : Negative charge resist phagocytosis. Bacteria that lose capsule-become avirulent
•Glycocalyx (Slime Layer)
–polysaccharide coating
–allows the bacteria to adhere firmly to various structures e.g. skin, heart valves, and catheters
–Pseudomonas aeruginosa- cystic fibrosis
–Staphylococcus epidermidis- endocarditis
–Streptococcus mutans-dental plaque and caries
–polysaccharide coating
–allows the bacteria to adhere firmly to various structures e.g. skin, heart valves, and catheters
–Pseudomonas aeruginosa- cystic fibrosis
–Staphylococcus epidermidis- endocarditis
–Streptococcus mutans-dental plaque and caries
- Flagella
Subunit: Flagellin
–Energy provided by ATP
–Spirochetes have flagellum like-axial filament
- Importance for two reasons
- -UTI causing bacteria move up in bladder
- Lab identification using anti-sera e.g. Salmonella
- Pili (Fimbrae)
–Mainly in Gram –ve –
Two functions:
-Attachment of bacterium to specific receptor in human tissue
-Sex pili form attachment during conjugation