Immobilization of Arsenite and Ferric Iron by Acidithiobacillus ferrooxidans and Its Relevance to Acid Mine Drainage

Abstract

Weathering of the As-rich pyrite-rich tailings of the abandoned mining site of Carnoulès (southeastern France) results in the formation of acid waters heavily loaded with arsenic. Dissolved arsenic present in the seepage waters precipitates within a few meters from the bottom of the tailing dam in the presence of microorganisms. An Acidithiobacillus ferrooxidans strain, referred to as CC1, was isolated from the effluents. This strain was able to remove arsenic from a defined synthetic medium only when grown on ferrous iron. This A. ferrooxidans strain did not oxidize arsenite to arsenate directly or indirectly. Strain CC1 precipitated arsenic unexpectedly as arsenite but not arsenate, with ferric iron produced by its energy metabolism. Furthermore, arsenite was almost not found adsorbed on jarosite but associated with a poorly ordered schwertmannite. Arsenate is known to efficiently precipitate with ferric iron and sulfate in the form of more or less ordered schwertmannite, depending on the sulfur-to-arsenic ratio. Our data demonstrate that the coprecipitation of arsenite with schwertmannite also appears as a potential mechanism of arsenite removal in heavily contaminated acid waters. The removal of arsenite by coprecipitation with ferric iron appears to be a common property of the A. ferrooxidans species, as such a feature was observed with one private and three collection strains, one of which was the type strain.Weathering of sulfide-rich rocks results in the formation of highly acidic and heavy metal-laden effluents. At the abandoned Pb-Zn mining site of Carnoulès (southeastern France), the pyrite-rich tailings are subject to bioleaching. Consequently, the Reigous spring, which collects the seepage waters from the waste materials, is acid (pH 3) and contains high levels of solubilized metals (Fe, Zn, and Pb) but also extremely high arsenic (As) concentrations (250 mg liter Ϫ1 on average) (26, 27). The extremely high contents of this metalloid are lowered by 2 to 3 orders of magnitude between the bottom of the tailing dam and few hundred meters downstream. The presence in the sediments of bacteria coated with Fe-As-rich material suggested that arsenic attenuation was due to precipitation mechanisms mediated by microorganisms (24,25,26,27). Among them, Acidithiobacillus ferrooxidans was proposed to be involved in the removal of soluble arsenic (9,26,27,35). The role of microorganisms in arsenic attenuation in this ecosystem was evaluated by two different approaches: (i) an A. ferrooxidans strain was isolated from the effluent and its role in arsenic oxidation and/or precipitation was determined (this paper); (ii) arsenite oxidizing bacteria, one of which belongs to the Thiomonas genus, were isolated and characterized (K. Duquesne, A. Yarzabal, J. Ratouchniak, D. Muller, D. Lièvre-mont, M-C. Lett, and V. Bonnefoy, unpublished results).A. ferrooxidans is an acidophilic chemolithoautotrophic gram-negative bacterium commonly encountered in acid mine drainage. This bacterium is resistant to heavy metals and metallo...

In situ proteo-metabolomics reveals metabolite secretion by the acid mine drainage bio-indicator, Euglena mutabilis

“…First, it has been shown that the 'oversaturation' in dissolved oxygen (that is, 4200% saturation with the atmosphere) facilitates inorganic co-precipitation of arsenic and iron colloids (Brake et al, 2001a(Brake et al, , 2001b. Second, an increased concentration in dissolved oxygen may favor the development of aerobic species such as Thiomonas or Acidothiobacillus spp., both known to be dominant and involved in the bio-attenuation processes at the Carnoulès AMD Duquesne et al, 2003;Bertin et al, 2011). Photosynthetic metabolism of E. mutabilis may therefore affect directly and indirectly the metal precipitation processes observed in AMDs.…”

“…Bacteria related to Acidithiobacillus ferrooxidans and Thiomonas spp. have been shown to oxidize Fe(II) and As(III), respectively, leading to co-precipitation of less bio-available As-Fe complexes Duquesne et al, 2003;Bertin et al, 2011). Besides these two bacteria, the Carnoulès AMD prokaryotic community has also been shown to be dominated by five other bacteria, of which two are related to a novel phylum (Bertin et al, 2011).…”

Metabolic diversity among main microorganisms inside an arsenic-rich ecosystem revealed by meta- and proteo-genomics

“…This further supports a major role of Acidithiobacillus sp. bin (CARN5) in the iron oxidation observed at Carnoulès Duquesne et al, 2003;Morin et al, 2003). Interestingly, two cytochromes c synthesized by CARN7 were also identified in protein extracts (Supplementary Table S2b).…”

“…This natural process of attenuation seems to be mainly due to microbial metabolism, leading to the oxidation of iron and arsenic into Fe(III) and As(V), and their co-precipitation with sulfur. In addition, laboratory experiments suggest that bacteria belonging to Thiomonas or Acidithiobacillus genera are involved in this process in situ Casiot et al, 2003;Duquesne et al, 2003;Morin et al, 2003;Egal et al, 2009). However, 16S-based community analyses have revealed that other genera are present in this ecosystem (Duquesne et al, 2003(Duquesne et al, , 2008Bruneel et al, 2003Bruneel et al, , 2006Bruneel et al, , 2008Bruneel et al, , 2011.…”

Structural and functional genomics of plasmid pSinA of Sinorhizobium sp. M14 encoding genes for the arsenite oxidation and arsenic resistance

“…They can transform soluble arsenite to less toxic form -arsenate, as well as catalyze oxidation of arsenic-bearing minerals like arsenopyrite (Rhine et al, 2008) or As (III) surfacebound to mineral sulfides (Duquesne et al, 2003). The process of arsenic oxidation catalyzed by bacteria is much faster than chemical oxidation (in the presence of O 2 ) and has been observed in many environments (e.g.…”