Question

The given graph represents the fastest multiplication rate of bacteria when they are added to rich broth.
The following graphs represent bacterial growth under different conditions, with increasing numbers of bacteria on the $y$-axis and increasing time on the $x$-axis.
Which of the given graphs shows growth in rich media on the addition of extra nutrients?

• A. 1
• B. 2
• C. 3
• D. 4
• E. 5

Answer 1

Answer: (C)

3

A bacterial cell undergoes several transitional changes when cultured on a nutrient media. These changes can be categorized as phases of growth. During initial stages when the bacteria adjust in the new environment, the nutrient uptake is slow due to low metabolic rate. This phase is known as the lag phase. As the metabolic rate increases the nutrient uptake increases along with it and the phase is known as log phase. When all the nutrient in the solution depletes the bacteria enters the stationary phase.

Here, in the above-given graphs, Graph 3 shows that the bacteria is dormant in the initial stages. But the growth rate shoots up suddenly which clearly indicates the addition of surplus nutrient which is needed in log phase.

So, option C is the correct answer.