There remains a need for rapid, specific and sensitive assays for the detection of bacterial indicatorsfor water quality monitoring. In this study, a strategy for rapid detection of Escherichia coli in drinkingwater has been developed. This strategy is based on the use of the substrate 4-methylumbelliferyl- _-d-glucuronide (MUG), which is hydrolyzed rapidly by the action of E. coli _-d-glucuronidase (GUD)enzyme to yield a fluorogenic 4-methylumbelliferone (4-MU) product that can be quantified and relatedto the number of E. coli cells present in water samples. In this study, the detection time requiredfor the biosensor response ranged between 20 and 120 min, depending on the number of bacteria inthe sample. This approach does not need extensive sample processing with a rapid detection capabil-ity. The specificity of the MUG substrate was examined in both, pure cultures of non-target bacterialgenera such as Klebsiella, Salmonella, Enterobacter and Bacillus. Non-target substrates that included 4-methylumbelliferyl- _-d-galactopyranoside (MUGal) and l-leucine _-naphthylamide aminopeptidase(LL _-N) were also investigated to identify nonspecific patterns of enzymatic activities in
E. coli. GUDactivity was found to be specific for E. coli and no further enzymatic activity was detected by otherspecies.
In addition, fluorescence assays were performed for the detection of E. coli to generate standardcurves; and the sensitivity of the GUD enzymatic response was measured and repeatedly determinedto be less than 10 E. coli cells in a reaction vial. The applicability of the method was tested by perform-ing multiple fluorescence assays under pure and mixed bacterial flora in environmental samples. Theresults of this study showed that the fluorescence signals generated in samples using specific substratemolecules can be utilized to develop a bio-sensing platform for the detection of E. coli in drinking water.Furthermore, this system can be applied independently or in conjunction with other methods as a partof an array of biochemical assays in order to reliably detect E. coli in water.