Ecotoxicological assessment using different bioassays for environmental sample are largely used this last 20 years. Among them, recombinant bioluminescent or fluorescent bacterial bioassays have been developed to determine the presence and the toxic effect of pollutants.

Chemical analyzes are sensitive and specific to detect pollutant, but they failed in the determination of bioaccessibility and biodisponibility of these contaminants. To overcome this problem, recombinant bioluminescent bacteria have been developed over the past years. These recombinant bacteria carry reporter genes for bioluminescence or fluorescence fused with gene promoters involved in metal resistance mechanisms.

Because of the lack of specificity of these recombinant bacteria, applications for environmental samples are limited. To deal with this problem, we used a set of bioluminescent recombinant bacteria sensitive to Metal Trace Element (MTE), which bioluminescence increases in the presence of MTE, leading to the quantification of bioavailable metals. In addition to these bioluminescent bacteria, we also used a collection of 1910 fluorescent recombinant bacteria, covering the majority of gene promoters of Escherichia coli K12 MG1655 strain, allowing a whole genome transcriptomics study.

Results obtained on complex environmental samples contaminated with metals (river water, chemical industry effluent, wood and soil leachates) showed gathering of samples based on the nature of their matrix. Using chemometric analyses, we are able to i) establish transcriptomics profiles related to the matrix, and ii) study variations of bacterial response according to the metallic contamination.

Because improvement of ecotoxicological assessment needs a large panel of bioassays, we propose a mixture of targeted and non-targeted high throughput arrays of bacteria to describe more realistically complex samples toxicity, combined with data mining interpretation.