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

The bioluminescence response of a genetically modified (lux-marked) bacterium to potentially toxic elements (PTEs) was monitored using an in vitro assay. Washed cells of Pseudomonas fluorescens were added to solutions containing various concentrations of metal salts. Bioluminescence, involving either plasmid or chromosomally encoded lux genes, declined as the metal concentration increased. The plasmid marked construct 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 chromosomally marked construct and Cu = Zn > Cd > Ni > Cr for the plasmid marked construct. The very sensitive response of lux-marked terrestrial bacteria to PTEs identified the potential for a rapid and flexible ecotoxicity assay for assessing the pollution of soil or fresh water environments.