Biosensors for rapid monitoring of primary-source drinking water using naturally occurring photosynthesis.

Working with primary-source freshwater drinking samples from the Clinch and Tennessee Rivers, we have developed a tissue-based biosensor detection system that uses naturally occurring aquatic photosynthetic tissue as the sensing material for detection of chemical antagonists in the water. Sensor readout is based on well-known principles of fluorescence induction by living photosynthetic tissue. The Clinch River is the main source of drinking water for Oak Ridge, Tennessee, while the Tennessee River is a major source for the city of Knoxville. We have successfully detected algae in every sample that we examined and readily monitored changes in the characteristic fluorescence induction curves when the samples were exposed to potassium cyanide (KCN), methyl parathion (MPt), N'(3,4-dichlorophenyl)-N,N-dimethylurea (DCMU), and paraquat. The percentage decreases in photochemical yields observed in Tennessee River samples after a 24-min exposure to KCN, MPt, and DCMU were, respectively, 21.89+/-0.76, 3.28+/-0.18, and 14.77+/-1.81. For a site at the Clinch River, the percentage decreases were 22.78+/-1.63, 8.32+/-0.21, and 17.71+/-1.32 (Table 1). The unique aspect of this approach to real-time water quality monitoring is that unlike conventional sensing devices, this sensor material is external to the detecting instrument and is continuously refreshed. These biosensors may be used as continuous rapid-warning sentinels for detection of chemical warfare agents in sunlight-exposed drinking water supplies.