A whole-cell bioreporter approach for the genotoxicity assessment of bioavailability of toxic compounds in contaminated soil in China

• Soils containing mitomycin C are found to be genotoxic to microorganisms.
• Samples from two environmentally fragile areas in China exert strong genotoxicity.
• Both free and adsorbed benzo[a]pyrene, mitomycin C, Cr and Pb exert genotoxicity.
• Acetic acid extracts of soil mimic the bioavailable fraction of Cr (VI) and Pb (II).
• A soil-water suspension bioreporter assay links bioavailability with genotoxicity.

A whole-cell bacterial bioreporter Acinetobacter baylyi strain ADP1_recA_lux that responds to genotoxins was employed to directly assess the adverse effects of the bioavailable fraction of mitomycin C (MMC), benzo[a]pyrene (BaP), chromium (VI) and lead (II) in amended soils and soil samples from two fragile areas in China without soil pre-treatment. The amended soils containing pollutants with the concentrations as low as 0.4 mg/kg MMC, 0.5 mg/kg BaP, 520 mg/kg Cr (VI) and 2072 mg/kg Pb (II) were found to be toxic. Soil particle-associated pollutants accounted for 86%, 100%, 29%, and 92% of the genotoxicity in the MMC, BaP, Cr (VI), and Pb (II) amended soil, respectively. The soils from contaminated sites were also valid to be genotoxic. The results suggest both free and soil particle-associated pollutants are bioavailable to soil organisms and a solid-phase contact bioreporter assay to soil contamination could provide a rapid screening tool for environmental risk assessment.