Coliforms are used as indicator organisms of sewage pollution because
a. They are pathogens.
b. They ferment lactose.
c. They are abundant in human intestines.
d. They grow within 48 hours.
e. All of the above.

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Understand the role of coliforms as indicator organisms: Indicator organisms are used to detect the presence of contamination, such as sewage pollution, in water or other environments.

Recall the characteristics of coliform bacteria: They are a group of Gram-negative, rod-shaped bacteria that are commonly found in the intestines of warm-blooded animals, including humans.

Analyze each option in the context of why coliforms are used as indicators:

a. They are pathogens – consider whether coliforms themselves cause disease or if their presence indicates contamination.

b. They ferment lactose – this is a key biochemical trait used to identify coliforms in laboratory tests, which helps in their detection.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Indicator Organisms in Water Quality Testing

Indicator organisms are microbes used to detect contamination in water, especially fecal pollution. They are chosen because their presence suggests potential pathogens, making water safety assessment more practical and efficient without testing for every pathogen.

Coliform Bacteria Characteristics

Coliforms are a group of Gram-negative, rod-shaped bacteria that ferment lactose with gas production within 48 hours at 35-37°C. Their ability to rapidly ferment lactose makes them easy to detect in water samples, serving as a reliable indicator of fecal contamination.

Abundance of Coliforms in Human Intestines

Coliform bacteria, especially Escherichia coli, are abundant in the intestines of humans and warm-blooded animals. Their presence in environmental samples indicates recent fecal contamination, which is why they are used as markers for sewage pollution.

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