Assessment of the interaction between microorganism and chemical mixture using resazurin reduction

The interaction between microorganism and chemical mixture was studied using resazurin reduction to delineate the microbial response to toxic substances. Two chemical mixtures, one consisting of two similar chemicals (2,3-dichlorophenol and pentachlorophenol) and another of two dissimilar compounds (mercuric chloride and 2,3-dichlorophenol), were tested on three pure bacterial isolates. Various toxicity patterns encompassing synergistic, neutral, and antagonistic effects on test bacteria were observed, demonstrating that the observed toxicity response from a chemical mixture does not always match the summed toxicity responses of the chemicals tested individually. No overall pattern regarding the interaction between microorganism and chemical mixture's toxicity could be drawn, implying that the traditional philosophy of setting water quality standards based on the toxicity assessment of individual chemicals should be readdressed to reflect the complexity of managing toxic substances in the aquatic environment.