Question

Which of the phase in the given diagram has least optical density?

• A. Lag phase
• B. Log phase
• C. Stationary phase
• D. Death phase

Answer 1

Answer: (D)

Death phase

The spectrophotometer measures the turbidity or optical density. Turbidity is the measure of the amount of light absorbed by a bacterial suspension. The degree of turbidity in the broth culture is directly proportional to the number of microorganism present i.e. microbial density. Increasing turbidity of the broth medium indicates an increase in the microbial cell mass and a decrease in cell mass is seen by a decrease in turbidity. Hence death phase will have the least optical density as cell lysis takes place during death phase.

So, the correct answer is option D.