Biosensing 2,4-dichlorophenol toxicity during biodegradation by Burkholderia sp RASC c2 in soil

Biodegradation of the model pollutant, 2,4-dichiorophenol (2,4-DCP) by Burkholderia sp. RASC c2, in contaminated sail was assessed by combining chemical analysis with a toxicity test using Escherichia coli HB101 pUCD607. E coli HB101 pUCD607 was previously marked with luxCDABE genes, encoding bacterial bioluminescence and was used as an alternative to Microtox. Mineralization of C-14-2,4-DCP (196.2 mu g g(-1) dry wt) in soil occurred rapidly after a 24 h lag. Correspondingly, 2,4-DCP concentrations in soil and soil water extra cts decreased with time and concentrations in the latter were at background levels (<0.12 mu g mL(-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 similar to 1.5 X control values in sail wafer 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 concentrations were 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. colt Lux-based E, coli was a sensitive biosensor of 2,4-DCP toxicity during biodegradation and results complemented chemical analysis.