Feasibility of using prokaryote biosensors to assess acute toxicity of polycyclic aromatic hydrocarbons

The aim of this study was to assess the acute toxicity of polycyclic aromat ic hydrocarbons using lux-marked bacterial biosensors, Standard solutions o f phenanthrene, pyrene and benzo[a]pyrene were produced using 50 mM hydroxp ropyl-beta-cyclodextrin solution which contained each respective polycyclic aromatic hydrocarbon at 6.25 times the aqueous solubility limit of the com pound. The polycyclic aromatic hydrocarbon solutions were incubated with ea ch of the biosensors for 280 min and the bioluminescence monitored every 20 min. Over the incubation time period, there was no significant decrease in bioluminescence in any of the biosensors tested with the exception of Rhiz obium leguminosarum biovar trifolii TAl luxAB. In this series of incubation s, there was a dramatic increase in bioluminescence in the presence of phen anthrene (2.5 times) and benzo[a]pyrene (3 times) above that of the backgro und control (biosensor without polycyclic aromatic hydrocarbon) after 20 mi n. Over the next 3 h, bioluminescence decreased to that of the control. An ATP assay was carried out on the biosensors to assess if uncoupling of the oxidative phosphorylation mechanisms in the respiratory chain of the cells had occurred. However, it was found that the polycyclic aromatic hydrocarbo ns had no effect on the organisms indicating that there was no uncoupling. Additionally, mineralisation studies using C-14-labelled polycyclic aromati c hydrocarbons showed that the biosensors could not mineralise the compound s. This study has shown that the three polycyclic aromatic hydrocarbons tes ted are not acutely toxic to the prokaryotic biosensors tested, although ac ute toxicity has been shown in other bioassays. These results question the rationale for using prokaryote biosensors to assess the toxicity of hydroph obic chemicals, such as polycyclic aromatic hydrocarbons. (C) 1998 Federati on of European Microbiological Societies. Published by Elsevier Science B.V . All rights reserved.