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.
DILUTIONS
Serial dilution:
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.