M3 Flashcards
Describe the common structural features of bacterial cell walls?
- Can be gram positive or gram negative
- Gram positive: thick peptidoglycan and plasma membrane
- Gram negative: outer membrane, thin peptidoglycan, plasma membrane
What is the function of bacterial cell walls?
- rigidity: determines shape
- protection against osmotic pressure
- selective permeability
- adhesion to surfaces
- Role in defence against infection: Recognition by host immune response, Important targets for antimicrobial drug action, Protection against phagocytosis
What are the common structural features of bacterial pili?
- Pilin protein, plus phosphate and glucose
- Mainly Gram negatives (can be positive)
What is the function of pili?
- Attachment & adherence to epithelial surfaces
- Sex pili: transfer genetic material: CONJUGATION
What are the common structural features of bacterial flagella?
- Gram positive and negative
- Flagellin protein
- Can have none, one, few or many
What is the function of a flagellum?
allow movement of motile organisms
What are the common structural features of bacterial capsules?
- Usually composed of polysaccharide
- Mucoid colonies – if lose capsule – rough colonies
- Can be well-defined capsule or less defined slime
- Surrounds an organism
What is the function of capsules?
- Forms a layer around the cell well
- Protects against recognition of surface antigens by host immune system
- Adherence to surfaces
- Inhibits phagocytosis
What is the difference between species and serotypes?
- Different species within a genus have significant differences at genetic and metabolic level
- Members of the same species have minor differences
- Different serotypes/strains of the same species have different phenotypic differences
How do bacteria divide?
Binary fission:
- Chromosome replicates, moves apart → Ring forms in middle of cell → New septum forms → Two identical daughter cells generated
How fast do bacteria divide?
Can be as quick as 15-30 mins
How is medically important bacteria growth different to environmental bacteria in terms of temperature?
- Medically important bacteria grow best at 35-37°C
- Environmental bacteria grow at different temperatures
What is a strict aerobe?
Requires oxygen to grow
What is a facultative anaerobe?
Can grow in presence or absence of oxygen
What is a strict anaerobe?
cannot grow in presence of oxygen
