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Escherichia coli are an indicator organism for fecal contamination and can represent a serious health hazard for humans. Common water quality tests are time consuming routine analysis. Our aim was the development of an automated biosensor for a fast identification and quantification of E. coli contaminations in ground-, surface-and drinking water. We applied an electrochemical assay to detect E. coli using their β-galactosidase activity. First, the enzyme production was stimulated in the cells and further, specifically released through a T2 bacteriophage mediated cell lysis. The enzyme concentration was monitored by potentiometric measurements. By using this methodological approach we were able to specifically detect at least 2 colonyforming units (CFU) of E. coli within 8 hours. The incorporation of this method into an automatic biosensor device would ensure the quality of our water. Furthermore, a continuous monitoring could be achieved and online data transfer ensures fast counteractions in water treatment plants. For future applications we developed a low-cost potentiostat with an easy-to-use PC software for environmental measurements and evaluated it with 3 different devices.

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