The detection of neurotoxicant activity by a bacterial toxicity assay

We present and evaluate a simple, rapid (2 hrs), colorimetric assay for the detection of toxicants, including neurotoxicants. The assay is based on the ability of toxicants to inhibit the de novo synthesis of an inducible enzyme, beta-galactosidase, by a rough mutant of E. coli, which is highly sensitive to a wide spectrum of toxic substances. The test is performed under stress conditions for the bacterium, since under such conditions better sensitivity for low concentrations of analytes is obtained. In the assay, the sample is mixed with the stressed bacteria and a cocktail containing the specific inducer for the chromogenic enzyme and factors essential to the recovery of the bacteria from their stressed condition. The ability of cells to synthesize B-galactosidase under these conditions depends on their ability to recover from the stress. Toxic materials interfere and/or inhibit the recovery process and with it the synthesis of beta-galactosidase.