Which of the following is an example of a metabolic activity that could be used to measure microbial growth!
A sucrose consumption
B turbidity
C standard plate count
D most probable number (MPN)
The correct answer and explanation is :
Correct Answer: A. Sucrose consumption
Explanation:
Microbial growth refers to the increase in the number of cells in a microbial population. While there are several methods to measure this growth, they can be classified into direct and indirect methods. Among these, metabolic activity is considered an indirect method of measuring microbial growth because it relies on assessing the biochemical activity of microorganisms rather than counting the cells themselves.
Option A: Sucrose consumption – Correct Answer
This is an example of a metabolic activity that can be used to indirectly estimate microbial growth. Microorganisms consume nutrients such as sugars (e.g., sucrose) during their metabolic processes to produce energy and build cellular components. By measuring how much sucrose has been consumed over time, scientists can infer the rate of microbial growth. As the microbial population increases, the rate of nutrient consumption also increases, indicating active metabolism and proliferation. This is especially useful in fermentation industries and biochemical studies, where substrate utilization reflects microbial activity.
Option B: Turbidity – Incorrect
Turbidity measures the cloudiness or optical density of a liquid culture. It is a quick, indirect method that estimates microbial growth by evaluating how much light is scattered by cells in suspension. Although related to growth, turbidity is not a measure of metabolic activity but rather of cell mass or concentration.
Option C: Standard Plate Count – Incorrect
This is a direct method of measuring microbial growth. It involves diluting a sample, plating it on nutrient agar, and counting the number of colony-forming units (CFUs). It gives an accurate count of viable microorganisms but does not assess metabolism.
Option D: Most Probable Number (MPN) – Incorrect
This is another direct method based on statistical estimation of cell numbers using serial dilution and growth in broth media. It estimates microbial numbers but doesn’t directly measure metabolic activity.
In summary, sucrose consumption reflects metabolic activity, making Option A the best answer for measuring microbial growth through a metabolic method.