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
What is a aerotolerant anaerobe?
Grows in absence of oxygen, can tolerate oxygen at low concentrations
What is microaerophilic?
Prefers low oxygen concentration
What is capnophilic?
Prefers higher carbon dioxide concentration
What is fermentation?
When bacteria utilises carbohydrates in absence of oxygen
