Biodegradation of the model pollutant, 2,4-dichlorophenol (2,4-DCP) by Burkholderia sp. RASC c2, in contaminated soil was assessed by combining chemical analysis with a toxicity test using Escherichia coli HB10 pUCD607. E coli HB101 pUCD607 waspreviously marked with IuxDABE genes, encoding bacterial bioluminescence and was used as an alternative to Microtox. Mineralizauco of 14{sup}C-2,4-DCP (196.2μg{sup}-1 dry wt) in soil occurred rapidly after a 24 h lag. Correspondingly, 2,4-DCPconcentrations in soil and soil water extracts decreased with time and concentrations in the latter were at background levels (<0.12μg mL{sup}-1) after day 2. Toxicity of soil water extracts to the lux-based biosensor also decreased with time. Mean light output of E. coli was stimulated by～1.5 X control values in soil water extracts when concentrations of 2,4-DCP were approaching the limit of detection by HPLC but returned to values equivalent to those of controls when soil water 2,4-DCP concentrationswere below the detection limit No mineralization or microbial growth was detected in noninoculated microcosms 2,4-DCP concentration in sterile controls decreased significantly with time as did toxicity to E. coli. Lux-based E. coli was a sensitivebiosensor of 2,4-DCP toxicity during biodegradation and results complemented chemical analysis.
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