Bioluminescent Reporter Bacterium for Toxicity Monitoring in Biological Wastewater Treatment Systems

Abstract

Toxic shock due to certain chemical loads in biological wastewater treatment systems can result in death of microorganisms and loss of floc structure. To overcome the limitations of existing approaches to toxicity monitoring, genes encoding enzymes for light production were inserted to a bacterium (Shk 1) isolated from activated sludge. The Shk 1 bioreporter indicated a toxic response to concentrations of cadmium (0.01 to 10 000 mg/L), 2,4‐dinitrophenol (0.01 to 1 000 mg/L), and hydroquinone (0.01 to 10 000 mg/L) by reductions in initial levels of bioluminescence on exposure to the toxicant. The decrease in bioluminescence was more severe with increasing toxicant concentration. Bioluminescence did not decrease in response to ethanol concentrations up to 10 000 mg/L or to pH conditions between 6.1 and 7.9. A continuous toxicity monitoring system using this bioreporter was developed for influent wastewater and tested with hydroquinone. The reporter exhibited a rapid and proportional decrease in bioluminescence in response to increasing hydroquinone concentrations.