Learning Module - Experiment 2A
Bacterial growth is logarithmic:
Optical Density is a measure of transmitted light:
Absorbance (O.D.) is proportional to cell number over a limited range.
There are four phases in bacterial growth:
- LAG phase - cells recover from stationary phase
- EXPONENTIAL (LOG) phase - cells are dividing by binary fission
- STATIONARY phase - nutrients have been consumed and cells stop growing
- DEATH phase - cells die (and subsequently lyse) from lack of food and accumulation of toxic waste products
Doubling time is the time it takes for the O.D. to double.
Overall dilution is the product of the individual dilutions.
A 1:10 or ten-fold dilution:
If there are 100 cells / mL in the first tube, then there are 10 cells / mL in the second tube.