Growth of microorganisms in a liquid culture

Question 1

How can a light sensor be used to measure the rate of growth of microorganisms?

Answer 1

Set up the microorganism culture between a light source and light sensor. As microorganisms increase, turbidity increases. Less light passes through and is detected by the sensor.

Question 2

How can a colorimeter be used to measure the rate of growth of organisms?

Answer 2

As microorganisms increase in solution, the turbidity of the solution increases, less light passes through and absorbance increases.

Question 3

How is the growth rate of the microorganism measured?

Answer 3

Transfer a sample from the microorganism culture to a cuvette at intervals. Use a data log to record absorbance.

Question 4

As the age of the culture increases, how does the absorbance vary?

Answer 4

The absorbance increases to a maximum and then remains constant.

Question 5

How can a cell count be found?

Answer 5

Stain the yeast suspension with methylene blue and view in a haemocytometer to find the cell density.
Multiply cell density by total volume for cell count.

Question 6

State the hazards and safety precautions involved in this practical.

Answer 6

Yeast may cause an allergic reaction. Avoid contact with skin and use aseptic techniques.