Bacteria Flashcards
what is a lipopolysaccharide (endotoxin)? why is it important?
- important virulence factor for evading phagocytosis
- barrier to certain antibiotics (like penecillin)
what is the difference in structure of gram positive and negative bacteria?
positive has thicker PEPTIDOGLYCAN, Negative has lipopolysaccharide layer
what is a glycocalyx/extracellular polymeric material?what is its function?
sticky substance made of polysaccharides/peptides.
it functions in survival (immune evasion of pathogens) and forming biofilms (attachment and communication). Protects against dehydration and stops nutrients leaving the cell
what is the difference between a capsule and slime layer?
capsule-firmly attached and highly organised
slime layer-unorganised and loosely attached
what is the structure of flagella?
- LONG SPIRAL FILAMENT made of FLAGELLIN. acts as propellor
- attached to motors that drive their rotation
- hook attached to basal body
what is an endospore?
dormant form of bacterium that is highly resistant to adverse environmental conditions (eg UV, irridation,, desiccation)
hoe do bacteria divide?
binary fission
what is generation time?
time taken for one cell to become 2
what are the phases of bacterial growth?
lag, log(exponential), stationary, (death)
what happens in lag phase?
- slow growth
- chemical composition of cells changes in prep for exponential growth
what happens in exponential (log) phase?
- cells grow at maximum doubling time
- nutrients in excess
- nutrients are consumed and TOXIC PRODUCTS released
- O the env no longer supports rapid growth
what happens in stationary phase?
- numbers = stable
- new cells= dying cells
what happens in the death phase?
cell death > cell growth
what are methods of directly counting bacterial cells?
- microscope
- flow cytometer (cells passing through a light detector)
- plate counts (cultivation)
what are methods of indirectly measuring bacterial growth?
- optical density (turbidity)
- measure respiration rate
