Question

If you have a dense laboratory culture of bacteria in a petri dish what is the best measure to report its density?

Answer 1

Population density can be defined as the number of individuals in a given area or volume. The most appropriate way of calculating population density is to find the relative densities of the population since in many cases absolute numbers are difficult to find.

Population density of bacteria in the culture can be measured in the following ways:-

• Taking a little of the colony and using a microscope to count the number of cells. A rough estimate can be found out.
• Dilution method: In case of a liquid culture, the culture is first diluted and the dilution of the culture is placed on the growth medium. The number of colonies is then counted and multiplied with the appropriate dilution factor.
• Turbidity measurement: The ‘cloudiness’ of the liquid culture is measured.