Which of the following living microorganism is used as an indicator of water pollution

The microorganism that is commonly used as an indicator of water pollution is Escherichia coli (E. coli). This bacterium is found in the intestines of warm-blooded animals, including humans, and its presence in water is an indication of fecal contamination.

Here are the steps to determine water pollution using E. coli:

1. Collect a water sample: The first step is to collect a sample of the water that you want to test. This should be done in a sterile container to avoid contamination.

2. Culture the sample: The next step is to culture the sample. This involves adding a growth medium that encourages the growth of E. coli and incubating the sample at a specific temperature for a certain period of time.

3. Count the colonies: After incubation, the sample is examined for the presence of E. coli colonies. These can be identified by their size, shape, and color.

4. Interpret the results: The number of E. coli colonies found in the sample is then compared to a standard to determine if the water is polluted. If the number of colonies is above the standard, the water is considered to be polluted.

5. Repeat the test: To ensure accuracy, the test should be repeated several times and the results averaged.

Remember, the presence of E. coli in water indicates that there may be other harmful bacteria, viruses, and parasites present as well. Therefore, it's important to treat or boil water that has tested positive for E. coli before consuming it.