Question

Discuss any three ways that can be employed to measure microbial cell growth.

Hint:

Make sure to remember that there are various ways to measure microbial growth, including both direct and indirect methods.

Answer 1

Viable Plate Count Method: In this method, the number of living cells in a microbial culture are counted by the number of colonies that grow after being plated in a petri dish. The colony forming units (CFUs) give a measure of how many cells are growing in the original culture. 
Turbidity Measurement: A spectrophotometer can be used to measure the turbidity or optical density of a microbial culture. The absorbance of the culture at a certain wavelength is proportional to cell concentration. This method is useful for quick and easy estimation of cell density. 
Coulter Counter: A Coulter counter is a device that can count cells directly as they pass through a narrow pore. This provides a direct reading of the cell number, and is often used to measure cell count in a suspension. 
Dry Weight: In this technique, the weight of the fixed volume of culture is measured after drying. It gives a direct estimate of the biomass. 
Wet Weight: Here, the wet weight of a fixed volume of the culture is directly measured. 
ATP Measurement: ATP concentration in a cell culture is measured by using ATP bioluminescence assay.