Microbial growth
- is the increase in number of cells not cell size.-Microbial growth is usually studied as a population not an individual. Individual cells divide in a process called binary fission where two daughter cells arise from a single cell. The daughter cells are indentical except for the occassional mutation.
the requirements for microbial growth
A) physical requirements
1.1) TEMPERATURE
PSYCHROPHILES PSYCHROTROPHS MESOPHILES THERMOPHILES HYPERTHERMOPHILES |
MINIMUM TEMPERATURE-5C
0C 15C 45C 65C |
OPTIMUM TEMPERATURE10C
20C 37C 60C 98C |
MAXIMUM TEMPERATURE15C
30C 45C 80 110C |
1.2) pH
-most bacteria grow bet. 6.5 & 7.5
- OSMOTIC PRESSURE
CHEMICAL REQUIREMENTS
- Carbon
- Nitrogen
- Sulfur
- Phosphorus
- Trace elements
measuring microbial growth
Direct methods
Plate counts Filtration MPN (Most Probable Number) Direct microscopic count Dry weight |
Indirect methods
Turbidity Metabolic activity Dry weight |