ASSESSMENT OF BIOAVAILABILITY OF HEAVY-METALS USING LUX MODIFIED CONSTRUCTS OF PSEUDOMONAS-FLUORESCENS

The bioluminescence response of a genetically modified (lux-marked) ba cterium to potentially toxic elements (PTEs) was monitored using an in vitro assay. Washed cells of Pseudomonas fluorescens were added to so lutions containing various concentrations of metal salts. Bioluminesce nce, involving either plasmid or chromosomally encoded lux genes, decl ined as the metal concentration increased. The plasmid marked construc t was significantly more sensitive to all metals except Cr. The order of metal sensitivity was found to be Cu = Zn > Cd > Cr > Ni for the ch romosomally marked construct and Cu = Zn > Cd > Ni > Cr for the plasmi d marked construct. The very sensitive response of lux-marked terrestr ial bacteria to PTEs identified the potential for a rapid and flexible ecotoxicity assay for assessing the pollution of soil or fresh water environments.