Coliforms are a group of bacteria commonly found in the environment, including soil, water, and the intestines of warm-blooded animals. They are often used as indicators of water quality, as their presence can suggest contamination by fecal matter, which may carry harmful pathogens. There are three main types of coliforms: total coliforms, fecal coliforms, and E. coli. While most coliforms are harmless, the presence of E. coli can indicate a higher risk of disease. Testing for coliforms is essential for ensuring the safety of drinking water and recreational water sources.