STRESS-INDUCIBLE TRANSGENIC NEMATODES AS BIOMONITORS OF SOIL AND WATER-POLLUTION

This paper reviews the current status of nematodes with stress-inducib le transgenes as biosensors responsive a range of external stressors, e.g., soil or water pollution, microwave radiation or immunological at tack. Transgenic Caenorhabditis elegans carrying reporter genes under heat shock promoter control express reporter products only under stres sful conditions. Although relatively insensitive to single metal ions, these worms respond to complex mixtures present in metal-contaminated watercourses and to laboratory mixtures containing similar constituen ts, but not to any of their components singly at comparable concentrat ions. Responses to metal mixtures are enhanced by a non-ionic surfacta nt, Pluronic F-127. Metals taken up by food bacteria and insoluble met al carbonates can also evoke stress responses, both in soil and aqueou s media. However, high concentrations of added metals are needed to in duce clear-cut responses in soil, owing to metal sorption onto clays a nd organic matter. Transgenic worms are also stressed by exposure to m icrowave radiation; pulsed signals generate responses that diminish ma rkedly with distance from the source. Finally, stress responses are in ducible by anti-epicuticle antisera and complement, suggesting that im mune attack can also activate the heat shock system. The development o f rapid microplate toxicity assays based on transgenic nematodes is di scussed.