A simple method for determining the toxicity of chemicals using a bacterial indicator organism

A method is described that can be used to assay the toxicity of chemicals using the bacterium Rhizobium meliloti 102f34 as the indicator organism. This bacterium can readily reduce the tetrazolium dye 3-(4,5-dimethyl thiazole-2-yl)2,5-diphenyl tetrazolium bromide. Reduction of the dye is followed with a spectrophotometer. Although 9 other bacteria were tested, R. meliloti was the only bacterium in which toxic chemicals inhibited reduction.