Question

In the scheme for microbiological testing for water,temperatures for taking colony count are ______
______\and ______\

• A. 42 C and 30 C
• B. 37 C and 30 C
• C. 30 C and 22 C
• D. 37 C and 22 C

Hint:

In water microbiology, colony counts are taken at 37 $^\circ\text{C}$ (to detect human/animal pathogens) and 22 $^\circ\text{C}$ (to detect environmental aquatic microflora).

Answer 1

The Correct Option is D

Step 1: Understanding the Concept:
In water quality monitoring, standard microbiological assays are designed to determine the sanitary quality of the water supply.
The colony count is a key parameter that estimates the total number of viable aerobic and facultative anaerobic bacteria present in a water sample.
To obtain a comprehensive profile, the assay is performed by incubating duplicate agar plates at two different temperatures: 37 $^\circ\text{C}$ and 22 $^\circ\text{C}$.

Step 2: Detailed Explanation:
Incubation at 37 $^\circ\text{C}$ is used to detect mesophilic bacteria, including those originating from the intestinal tract of humans and warm-blooded animals.
This count serves as an indicator of potential contamination by pathogens and poor hygienic handling of water.
Incubation at 22 $^\circ\text{C}$ is used to estimate the abundance of natural, non-pathogenic aquatic microflora that thrive at ambient environmental temperatures.
Comparing these two counts helps water quality managers assess whether the water treatment and filtration systems are operating correctly.
A sudden increase in either count indicates a failure in sanitation.
Therefore, 37 $^\circ\text{C}$ and 22 $^\circ\text{C}$ are the standard temperatures used.

Step 3: Final Answer
The two temperatures used for colony counts in water testing are 37 $^\circ\text{C}$ and 22 $^\circ\text{C}$.