Final answer:
The mechanism of E. coli test kits in water involves lactose broths with pH indicators that change color when E. coli ferments lactose, indicating its presence. Reagents include these broths and pH indicators, and more advanced systems might use software-analyzed panels of reactions for identification.
Step-by-step explanation:
The mechanism of test kits designed to detect E. coli in water typically involves a biochemical reaction based on the bacterial metabolism. These tests utilize lactose broths with pH indicators that exhibit a color change when E. coli ferments the lactose, indicating the presence of this bacterium. As E. coli ferments the lactose, the pH of the medium changes, leading to the color transition from red to yellow. Therefore, the reagents usually involved in these test kits include a lactose broth with a pH indicator.
Additionally, more advanced identification systems, like Biolog, may use a panel of biochemical reactions analyzed by software, which also includes pH and chemical sensitivity changes. While the exact chemicals used can vary, they generally involve those that react to the bacteria's metabolic processes. For identifying specific bacteria such as E. coli, selective and differential media that prompt a biochemical reaction (such as a color change) upon bacteria growth are employed.