Coliform bacteria are a group of microorganisms commonly found in the environment, including soil, water, and the intestines of warm-blooded animals. They are used as indicators of water quality, as their presence suggests that harmful pathogens may also be present. These bacteria are generally not harmful themselves, but their detection in drinking water or recreational water sources can signal potential contamination. Testing for coliform bacteria helps ensure the safety of water supplies and protects public health from waterborne diseases.