2. Direct count It involves direct microscopic counting of bacteria in the sample using counting chamber. It is relatively quick and does not need the sample to be incubated.
Procedure . Serial dilution of the sample . Fill known area and volume of the counting chamber with the sample . Total number of bacteria in the sample per unit volume is equal to No. of bacteria in the sample Χ the No. of squares Χ dilution factor.
3. Turbidimetric method It is the method of determination of bacterial growth in liquid media. Bacterial growth increases the turbidity of liquid to absorb light. The turbidity of the suspension is determined by spectrophotometer.
Factors influencing bacterial growth in vitro Not all bacterial species grow under identical environmental conditions. Each bacterial species has a specific tolerance range for specific environmental parameters. Out side the tolerance range environmental conditions for a bacteria to reproduce, it may survive in dormant state or may lose viability. Rates of bacterial growth are greatly influenced by the following environmental parameters.
. Nutrition . Temperature