Toxicity of mono-, di- and tri-chlorophenols to lux marked terrestrial bacteria, Burkholderia species Rasc c2 and Pseudomonas fluorescens

Burkholderia species RASC and Pseudomonas fluorescens were marked with lux genes, encoding for bioluminescence and used to assess the toxicity of mono -, di- and tri-chlorophenols by determining the decline in bioluminescence following exposure to the compounds in aqueous solution. Toxicity was expre ssed as a 50% effective concentration value (EC50), equating to the concent ration of compound which caused a 50% decline in bioluminescence. Comparing the toxicity values of the compounds showed that, in general, increasing t he degree of chlorination, increased toxicity. By carrying out forward mult iple linear regressions with log(10) EC50 values and physio-chemical descri ptors, it was shown that molecular parameters describing the hydrogen bondi ng nature of a chlorophenol provided a better fit than regressions between toxicity data and log(10) K-ow alone. Utilising these descriptor variables in equations, it was shown that the toxicity of chlorophenols to the lux ma rked bacteria could be predicted from the compounds physio-chemical charact eristics. By correlating lux marked RASC c2 and P. fluorescens EC50 values with toxicity values using Pimephales promelas (fathead minnow), Tetrahymen a pyriformis (ciliate) and marine bacterium Vibrio fischeri, it was apparen t that lux marked RASC c2 correlated well with the freshwater aquatic speci es (P. promelas and T. pyriformis). This implied that for predictions of to xicity of organic xenobiotic compounds to higher organisms, lux marked RASC c2 could be utilised as a rapid surrogate. (C) 2001 Elsevier Science Ltd. All rights reserved.