Microbial Growth Flashcards
Define the cell cycle
Complete sequence of events from the formation of a new cell through to the next division
What are the 3 stages in the cell cycles
- Period of growth after cell is born
- Chromosome replication and partitioning
- Cytokinesis
What triggers stage 2
Increase in cell mass
What is septation
Formation of a cross wall between 2 daughter cells
What is a batch culture
incubation of a sample in a closed vessel with a single batch of medium
What are cells doing during the lag phase
Adapting to the environment and growing
Describe the growth rate in the log phase
Constant and maximal
What 2 rates are equal in the stationary phase - give 2 reasons for this
Cell division and cell death
nutrient limitation and toxic waste accumulation
What is happening during the death phase - give 2 hypotheses
Cell death declines exponentially
Cells are dormant and capable of new growth in right conditions
Fraction of the population undergo programmed cell death
What is occurring during long term stationary phase
natural selection - waves of genetically distinct variants
How is the growth rate constant (k) and the generation time linked
k is the reciprocal of the generation time
What is a continuous culture - give 1 advantage
Culturing cells in a way that culture conditions remain constant over extended periods of time
Allows study of microbial growth at low nutrient concentrations similar to those of the cell’s natural environment
Define dilution rate - what does it control
Rate at which the medium flows through the vessel - growth rate
What does the turbidostat measure
Turbidity - amount of light scattered
How does the cell biomass differ in the chemostat and turbidostat - what dilution rates do they work best at
Chemostat - limiting nutrient controls concentration - lower
Turbidostat - biomass is kept constant - higher
