Question

Upon inoculation into a new nutrient medium, the bacteria shows four distinct phases of growth. Arrange these phases according to the order they occur:
(A) Log phase
(B) Phase of decline
(C) Stationary phase
(D) Lag phase
Choose the correct answer from the options given below:

• A. (A), (B), (C), (D).
• B. (D), (A), (C), (B).
• C. (B), (A), (D), (C).
• D. (C), (B), (D), (A).

Hint:

Remember the growth curve sequence using the initials: Lag \(\rightarrow\) Log \(\rightarrow\) Stationary \(\rightarrow\) Death (Decline).
- Lag: Getting ready (0 net growth).
- Log: Exponential explosion (maximum growth).
- Stationary: Flat line (growth = death).
- Decline: Falling population (death $>$ growth).

Answer 1

The Correct Option is B

Step 1: Understanding the Concept:
When bacteria are inoculated into a closed liquid culture medium (batch culture), they exhibit a predictable, characteristic pattern of population growth over time.
This pattern is represented by the bacterial growth curve, which is divided into four distinct sequential phases.

Step 2: Detailed Explanation:
Let us review the four phases of the bacterial growth curve in chronological order:
1. Lag Phase (D): Immediately following inoculation, there is no immediate increase in cell number.
The bacteria are adapting to their new physical and chemical environment, synthesizing essential enzymes, cofactors, and structural components.
2. Log (or Exponential) Phase (A): During this phase, the adapted bacteria grow and divide at their maximum rate under the given conditions.
The population increases exponentially (logarithmically), and the generation time reaches its shortest and most constant value.
This is the phase of peak metabolic activity.
3. Stationary Phase (C): As nutrients are depleted and toxic metabolic waste products accumulate, the growth rate begins to slow.
The rate of new cell production eventually equals the rate of cell death, resulting in a stable, constant population size.
4. Phase of Decline (or Death Phase) (B): With the complete depletion of energy sources and the accumulation of toxic wastes, the environment becomes unsustainable.
The cells die at an exponential rate, and the viable cell count declines.
Therefore, the correct chronological sequence is Lag phase \(\rightarrow\) Log phase \(\rightarrow\) Stationary phase \(\rightarrow\) Phase of decline, which corresponds to the order: (D), (A), (C), (B).

Step 3: Final Answer:
The correct option is (B).