Final answer:
Counting fecal coliforms in a water sample is used to assess water quality and indicate potential fecal contamination. The MPN method helps determine the most probable number of viable bacteria, which is crucial for ensuring water safety.
Step-by-step explanation:
The number of fecal coliforms in a water sample is counted to assess water quality and determine the level of fecal contamination, which may pose a health risk due to potential pathogens. Fecal coliforms, such as E. coli, are bacteria that originate in human and animal fecal waste and their presence in water is an indication of pollution and possible presence of pathogens. The most probable number (MPN) method is a statistical procedure used to estimate the viable microorganisms in a sample, and is particularly useful for testing water quality when the number of organisms is too low to be reliably counted by other methods. Counting fecal coliforms is an indirect method of estimating bacterial counts, which involves observing changes in medium due to bacterial metabolism through color changes or turbidity, indicating growth and serving as a measure of water safety and suitability for consumption or recreation.