Tennessee Wastewater Operator Practice Exam

What is the distinguishing factor for fecal coliform bacteria compared to total coliform bacteria?

1. Growth on nutrient agar

2. Growth on M-FC media at 44.5 degrees Celsius

3. Production of gas at 35 degrees Celsius

4. Presence of specific enzymes

The correct answer is: Growth on M-FC media at 44.5 degrees Celsius

The distinguishing factor for fecal coliform bacteria compared to total coliform bacteria is their ability to grow on M-FC media at 44.5 degrees Celsius. This selective growth condition is used to identify fecal coliforms specifically, which are typically associated with warm-blooded animals' fecal material. The ability to thrive in this elevated temperature distinguishes fecal coliforms from other types of coliform bacteria, which may not grow as well under these conditions. M-FC media contains specific nutrients that promote the growth of fecal coliforms while inhibiting the growth of many non-fecal coliforms. The incubation at 44.5 degrees Celsius is crucial, as it reflects the typical environmental conditions these bacteria are suited for, providing a reliable means of differentiating the two groups based on their thermal tolerance and growth characteristics. This method is vital in wastewater treatment and monitoring, where the presence of fecal coliforms indicates potential contamination from sewage or animal waste, posing health risks to humans and the environment. Other methods and criteria, such as growth on nutrient agar or gas production at certain temperatures, do not provide the same clear distinction between fecal and total coliforms.