A presence/absence coliform test utilizes which of the following?

The presence/absence coliform test is a specific method used to determine whether coliform bacteria are present in a water sample. This test typically relies on a color change to indicate the presence of these bacteria.

In this method, a growth medium is used that contains nutrients favorable for coliform bacteria as well as a dye. If coliforms are present in the sample, they will metabolize the nutrients and lead to a color change in the medium. This visual indication simplifies the process of determining water quality—if the color changes, it confirms the presence of coliform bacteria.

Understanding the significance of this color change is essential for water quality monitoring since coliforms can serve as indicators of potential contamination and the possible presence of harmful pathogens. This test provides a straightforward, quick assessment, which is crucial for ensuring safe drinking water.

Other methods mentioned, like temperature change, electrochemical signals, and pH changes, do not align with the standard procedures for presence/absence testing for coliforms and would typically apply to other types of water quality assessments.