A NEWLY DEVELOPED CONTINUOUS TOXICITY TEST SYSTEM USING A LUMINOUSLY MODIFIED TERRESTRIAL BACTERIUM

Freshwater borne bacteria transformed with luxAB-containing plasmid were optimized for the toxicity tests of various organic carbons and heavy metals. The EC$\sub$50/ values obtained from tests using the most sensitive bacterium to toxicants, YH9-RC, revealed to be much less than those from the Microtox$\^$/. In addition, some physiological characteristics of this bacterium under the toxic stress conditions such as potential bioluminescence, specific growth rate, and intracellular ATP contents, reproducibly and reliably correlated to the toxicity of the chemicals exposed. The higher concentrations of COD in wastewater samples, the lower EC$\sub$50/ values, therefore the developed toxicity test was found to be easily applicable to the toxicity test for wastewater samples and effluents. The conditions for constructing 384-multiwell plate containing freeze-dried bacterium were also optimized through the addition of 0.16 M trehalose before freeze-drying. Consequently, the advanced test system featuring a continuous measurement of the toxicity, an automated real-time monitoring of its results, and an alerting function was designed and constructed in combination with the microbiological, mechanical, and electronic compartment.