Bacterial community structure and functional arrA gene diversity associated with arsenic reduction and release in an industrially contaminated soil
Abstract
This study aimed at evaluating potential arsenic (As) mobility in an industrially contaminated
soil (64 mg As kg-1) of the Meuse River basin, and at identifying key bacterial groups that drive soil As dynamics. Both speciation and release of As from this soil was followed under anaerobic
conditions using a laboratory batch experiment. In the presence of exogenous carbon sources,
AsV initially present in the soil matrix and/or adsorbed on synthetic hydrous ferric oxides was
solubilized and mainly reduced into AsIII by indigenous soil microfora. After a one-month
incubation period in these biotic conditions, AsIII accounted for 80-85% of the total dissolved As
and more than 60% of the solid-phase As. Bacterial community structure (i.e. 16S rDNA-based
CE-SSCP profiles) changed with incubation time and As amendment. The detection of distantly
related arsenate respiratory reductase genes (arrA), as functional markers of AsV-respirers,
indicates that novel dissimilatory AsV-reducing bacteria may be involved in As
biotransformation and mobility in anoxic soils. Since As and iron were concomitantly released, a
crucial role of indirect As-mobilizing bacteria on As behavior was also revealed. Our results show that the majority of As within the soil matrix was bioavailable and bioaccessible for
heterotrophic AsV reduction to AsIII, which may increase As toxicity and mobility in the
contaminated soils.