Temperature is one of the most important factors influencing the sensitivity of bacteria to toxicants, but little work investigating the nature of the interaction between microbial cells, temperature and toxicants has been carried out. In this study a biosensor assay and an impedance spectroscopy assay were used to investigate different aspects of the temperature/toxicity interaction in Escherichia coli exposed to the model toxicant 3,5-dichlorophenol (3.5-DCP). The biosensor assay showed that E. coli metabolic rate increased significantly with increasing temperature, but the sensitivity of the cells to 3,5-DCP was significantly reduced at the higher test temperatures. The impedance assay indicated that whilst increasing temperature influenced the physiology of the E. coli cytoplasmic membrane, it had no significant effect on the sensitivity of the cells to 3,5-DCP. Overall the results of the two assays suggest that the manner in which temperature change influences E. coli sensitivity to 3,5-DCP is influenced by temperature induced changes in the metabolic rate of the cells, but not by changes in membrane physiology seen over the temperature range 15-35 degrees C. The use of two assays, measuring different biological endpoints was beneficial to examining the interaction between temperature and toxicity. (c) 2006 Elsevier Ltd. All rights reserved.