Growth Curve Flashcards
What are the 4 phases of the growth curve?
- lag phase
- exponential phase
- stationary phase
- death phase
What happens during lag phase?
Cells are not growing, they are adjusting to environment. They alter gene expression
What happens during exponential phase?
Cells divide at period of time to double mass in media. Slope is the specific growth rate constant (u) expressed as 1/time unit
What happens during stationary phase?
a. endospore formation
b. decrease in rate of metabolism
c. activation of stress response genes
d. formation of “persister cell” (not actively dividing)
What causes deceleration of growth?
parameters become limiting
building of inhibitory end-product of metabolism
change in pH
What happens during death phase?
Cells that cannot sporulate die due to nutrient deficiencies.
What is the growth equation?
Nt = No e^ (ut)
What metabolites follow growth curve? What about the other?
Primary metabolites follow growth curve
Secondary metabolites increase when you reach stationary phase
Batch versus continuous culture?
Batch: everything added at once
Continuous: nutrients continually added at slow rates
How can you determine cell densities?
- Direct cell counts (all cells)
- Viable cell counts (all alive cells)
- Biomass measurements
- Measure cell products
What are the direct cell count methods?
- Petroff-Hauser chamber (count cells in a grid)
- Coulter counter (measures disruptions in voltage current)
What are the viable cell count methods?
- Dilution and plating scheme (dilute and count colonies)
- Filter plating (put filter on petri dish)
- MPN (looks at +/- growth at 3 different dilutions)
What are the biomass measurement methods?
- Turbidity (use spectrometery to find optical density)
- Weigh cells (mass of pellet)
What cell products can you measure?
- Acid (pH probe)
- Gas (durham tube)
- ATP (luciferase reaction)
