Monitoring subtoxic environmental hazards by stress-responsive luminous bacteria

A novel approach to toxicant detection is described, based on monitoring bacterial reactions to environmental threats. In response to such stress, various defense mechanisms are turned on by initiating gene transcription at specific DNA sites known as promoters. To follow this transcription sensitively, such promoters were genetically fused in Escherichia coli to the lux (luminescence) genes from the bacterium Vibrio fischeri. The bacteria thus engineered now produce light in response to different environmental insults; this light is easy to measure and quantify. A wide range of promoters was utilized in this manner, to create over a dozen bacterial constructs that emit light in response to specific or general stress factors. The responses of four of these to defined chemicals and to wastewater samples are described. The threats reported by these bacteria include general and protein damage, DNA damage, and oxidative hazards (peroxides and oxygen radicals). Members of the tested panel exhibited very high sensitivity: generally, the luminescent response occurred at subtoxic doses of the stressing factor, and was evident within 20 min to 2 h after exposure. It is proposed that these bacteria, or others constructed in a similar manner, can serve as powerful early-warning indicators of environmental pollution, as well as monitoring tools for the operation of different industrial processes, from fermentation reactors to wastewater treatment plants.