Microbial Population Growth
BIOL 3104
Outline of Microbial Population Growth
See Internet site:
Bacterial Reproduction and Population Growth
Bacterial Growth Curve
Lag Phase
Growth Rate
Reproductive versus Death Rates
Acceleration Phase
Growth Rate
Reproductive versus Death Rates
Exponential Phase
Phase will continue until one of two things happens"
1.
2.
Growth Rate
Reproductive versus Death Rates
Customary to express the growth rate of a culture as generations per hour.
The number of generations per hour can be determined by plotting cell nmber against time on a semilog scale and reading off the time required for the number to double (e.g., binary fission)
If the generation time is 40 minutes, then what is the growth rate in generations per hour?
Can calculate the number of generations by g = (log N-log No)/log 2.
If you have an inoculum of 103 cells that grow exponentially to 109 cells, how many generations does it take?
If the growth required 13.3 hours, the growth rate was how many generations per hour?
How could you maintain cells in exponential phase?
1. Transfer them repeatedly into fresh medium of identical composition while they are still growing exponentially.
2. Chemostat
3. Turbidostat
Retardation Phase
Growth Rate
Reproductive versus Death Rate
Stationary Phase
Growth Rate
Reproductive versus Death Rate
Declining Phase
Growth Rate
Reproductive versus Death Rate
Measurement of Population Growth
Cell Density
Cell mass determination
Chemical analysis of nitrogen or proteins
Cell Concentration
Viable cell count
Colony counting
Colony Forming Units (CFU) = Bacterial Colony Count X Reciprocal of volume X Reciprocal of dilution
Organisms per ml of culture = Bacterial Colony Count X Reciprocal of dilution
Colony counting using membrane filter system
Photoelectric means using spectrophotometer
Determining Total Counts
Direct microscopic counts (Breed smear technique)
Proportional counting
Petroff Hausser counting chamger
Electronic counting