Texas Commission on Environmental Quality (TCEQ). Class C Water License Exam

What organism is commonly used as an indicator in bacteriological analysis of water?

1. E. coli

2. Salmonella

3. Coliform

4. Cryptosporidium

The correct answer is: Coliform

The choice of coliform bacteria as an indicator organism in bacteriological analysis of water is based on their presence indicating the potential contamination of water sources by fecal materials from warm-blooded animals. Coliforms are a group of bacteria, which includes various species such as E. coli, that are commonly found in the intestines of humans and animals. The presence of coliforms in water suggests that pathogens may also be present, posing a risk to human health. Using coliforms as an indicator is beneficial because they are relatively easy to detect and their growth can be easily quantified in a laboratory setting. This makes them a practical choice for routine monitoring of water quality. While E. coli specifically indicates fecal contamination, testing for general coliforms provides a broader assessment of water safety. Salmonella and Cryptosporidium, while important pathogens, are not typically used as indicator organisms for general water quality testing due to their specific pathogenic characteristics and the more complex methods required to detect them. Their presence in water does indicate contamination, but they do not serve as a reliable indicator for overall water quality. Thus, coliforms serve as a crucial preliminary indicator in bacteriological water testing.