ASSESSMENT OF TOXICOLOGICAL INTERACTIONS OF BENZENE AND ITS PRIMARY DEGRADATION PRODUCTS (CATECHOL AND PHENOL) USING A LUX-MODIFIED BACTERIAL BIOASSAY

A bacterial bioassay has been developed to assess the relative toxicit ies of xenobiotics Commonly found in contaminated soils, river waters, and ground waters. The assay utilized decline in luminescence of lux- marked Pseudomonas fluorescens on exposure to xenobiotics. Pseudomonas fluorescens is a common bacterium in the terrestrial environment, pro viding environmental relevance to soil, river, and ground water system s. Three principal environmental contaminants associated with benzene degradation were exposed to the luminescence-marked bacterial biosenso r to assess their toxicity individually and in combination. Median eff ective concentration (EC50) values for decline in luminescence were de termined for benzene, catechol, and phenol and were found to be 39.9, 0.77, and 458.6 mg/L, respectively. Catechol, a fungal and bacterial m etabolite of benzene, was found to be significantly more toxic to the biosensor than was the parent compound benzene, showing that products of xenobiotic biodegradation may be more toxic than the parent compoun ds. Combinations of parent compounds and metabolites were found to be significantly more toxic to the bioassay than were the individual comp ounds themselves. Development of this bioassay has provided a rapid sc reening system suitable for assessing the toxicity of xenobiotics comm only found in contaminated soil, river, and ground-water environments. The assay can be utilized over a wide pH range and is therefore more applicable to such environmental systems than bioluminescence-based bi oassays that utilize marine organisms and can only be applied over a l imited pH and salinity range.