Question

Coliforms and thermotolerant coliforms are indicator organisms. In approximately 400 words (total) answer both parts a and b: a. What is an indicator organism, and why do we use them in assessing water safety?

b. Define a coliform and a thermotolerant coliform. Which is a better indicator of faecal contamination? Justify your answer.

Answer 1

a. An indicator organism is such an organism that indicates the change in the environment, through changes in their growth pattern or metabolic activities. They can be used to indicate presence of pollutant in the water body, presence of pathogenic organisms, the health of the environment, etc. An important function of indicator bacteria is that, it can be used to determine water safety. Indicator bacteria, such as fecal coliforms, are normally present in the intestine of warm-blooded animals. Their presence in water bodies is a sign of fecal contamination. They are themselves non-pathogenic, but their presence indicates that other pathogenic organisms are present in the water and thus, the water is not fit for drinking and treatment measures need to be taken.

b. Coliform is a group of organisms that are widely present in the environment. These organisms are characterized by being gram negative, rod shaped, and their inability to form spores. They are lactose fermenters, and can produce acid and gas. They are present in soil, vegetation, fecal matter, etc.

Thermotolerant coliform is a type of coliform organism, that is non pathogenic, and is present in fecal matter of human and other warm blooded animals. For example, E.coli.

Thermotolerant coliforms are a better indicator of fecal contamination in water bodies. They are primarily present in feces, whereas, coliforms include organisms that can be present in both feces and soil. Therefore, presence of coliforms are not a clear indication of fecal contamination.