Influence of Heterotrophic Microbial Growth on Biological Oxidation of Pyrite

Abstract

The rate and extent of pyrite oxidation by the iron-oxidizing bacteria Acidithiobacillus ferrooxidans was limited by the growth of the heterotrophic microbe Acidiphilium acidophilum. In batch systems containing a mixture of both organisms, the maximum zero-order rate of ferric iron accumulation was about 1.4 mg of Fe3+ L(-1) d(-1) as compared to 9.4 mg of Fe3+ L(-1) d(-1) for pure cultures of A. ferrooxidans under the same conditions. Pyrite oxidation was limited in cases where both cultures of organisms were initially present as well as situations where the heterotrophic organisms were added to established, pyrite-oxidizing systems containing A. ferrooxidans. Results also indicated that organic carbon remaining in solution following heterotrophic bacterial growth reduced the rate of abiotic pyrite oxidation by the ferric ion. Furthermore, a cell-free solution of the residual organic carbon resulted in a lag of A. ferrooxidans growth in soluble ferrous medium. The residual organic carbon solution that accumulated during the growth of Aph. acidophilum had a diverse molecular weight distribution, indicating that different compounds could be responsible for the inhibition of chemical pyrite oxidation and the A. ferrooxidans growth lag observed. Titration of dissolved copper ions with residual dissolved organic carbon originating from Aph. acidophilum cultures indicated that a metal complexation mechanism could be responsible for the lower rates of pyrite oxidation observed. These data suggest that encouraging the growth of heterotrophic microorganisms under acid mine drainage conditions may be a feasible strategy for decreasing both the rate and the extent of sulfide mineral oxidation.

The co-culture of Acidithiobacillus ferrooxidans and Acidiphilium acidophilum enhances the growth, iron oxidation, and CO2 fixation

“…Many previous researches (Peccia et al 2000;Marchand and Silverstein 2002; on the mix culture of these two species showed excess glucose or other organic compounds added to the mix culture medium enhanced the heterotrophic growth of Aph. acidophilum, while the organic compounds added to liquid medium and the metabolites derived from the growth of heterotrophic bacteria led to cellular toxin to autotrophic growth of At.…”

“…On the one hand, previous researches on a mixed culture of these two strains showed that pure cultured At. ferrooxidans and its oxidation of ferrous iron and pyrite were inhibited by organic compounds (Marchand and Silverstein 2002;, while mix cultured with Aph. acidophilum permits to circumvent this inhibition.…”

Microbial Diversity and Community Assembly across Environmental Gradients in Acid Mine Drainage

“…Microorganisms can directly or indirectly utilize inorganic minerals as electron donors and irreversibly alter the physical conditions of the environments [33,34]. Pyrite (FeS 2 ) is the most abundant sulfide mineral on Earth and is an important player in the generation of mine drainage, as indicated by the following equations [6,35] …”

“…Owing to the increased concentration of Fe 3+ , the pyrite is sustainably dissolved, driving the primary production of mine drainage [21,34]. Thiosulfate, produced by pyrite oxidation at the original stage (with high ambient pH), can then also be oxidized by some bacteria and archaea (Equation (3)) [6].…”

“…and Acidiphilium spp. also thrive in AMD environments and influence the oxidation of pyrite, greatly increasing the diversity of microbial communities [34,42]. To date, the dominant lineages detected in AMD environments are Proteobacteria, Nitrospira, Actinobacteria, Firmicutes, Acidobacteria, Aquificae in bacteria and Euryarchaeota, Crenarchaeota in archaea, as summarized by Chen et al [22].…”