Microbiology Flashcards
Growth
Increase in number of cells
Generation time
Tine made for I cell to divide & form 2 cells
Why does bacteria culture growth plateu?
Nutrient become limiting
Toxins form
Lag phase of bacteria cycle
Cells adjust to new conditions, synthesis required metabolic enzyme & metabolites
Exponential phase
optimal growth with regular doubling in cell numbers
Stationary phase
growth limited by nutrient depletion or accumulation of toxin. No overall growth as production = death rate
Death phase
complex gradual loss of viability but with some cell turnover
Total cell count
Total number of bacterial cell
Viable cell count
Number of living bacterial all
How does plating methods work?
- Culture plates onto nutrient medium
- each colony represents progeny of single viable cell
-Only measures viable cells
Negatives of plating methods
- Underestimates for cells in chain or cluster
- number of colonies dependent on growth conditions
Turbidity methods how does it work?
- Measures light scattering cells
- simple convenient
- can be done continuously
Negatives of turbidity methods
- Low sensitive
- certain range to be accurate
Direct counting method - how does it work?
- Direct method
Count of known volume of culture
Accommodate clumping & chaining
Negatives of direct counting method
Doesn’t discriminate live / dead
Laborias
