Effect of metal concentration on the microbial community in acid mine drainage of a polysulfide ore deposit

Resumo

The composition of microbial communities of acid mine drainage (AMD) in two wells drilled in the terrace of the Sherlovaya Gora open-cast polymetallic ores mine (Eastern Siberia) was studied. While drainage water filling two wells, ShG14-1 and ShG14-8, had similar values of pH (2.6), Eh (447–494 mV), and temperature (6.5°C), the water in the first well contained more metals and sulfate. The water in ShG14-1 and ShG14-8 contained, respectively, 1898 and 434 mg/L of iron, 734 and 49 mg/L of manganese, 81 and 7 mg/L of copper, 3597 and 787 mg/L of zinc, and 15990 and 3632 mg/L of sulfate. Molecular analysis of the microbial communities was performed using pyrosequencing of the 16S rRNA gene fragments. The ShG14-8 microbial community included such bacterial taxa typically found in AMD sites as Gallionella (38.8% of total 16S rRNA gene sequences), Ferrovum (4.4%), Acidiphilium (9.1%), Acidisphaera (8.2%), Acidithiobacillus (7.2%), and Leptospirillum (4.6%). In the ShG14-1 sample with higher content of metals, strict acidophiles Acidithiobacillus (16.0%) and Leptospirillum (25.4%) were more abundant, while Gallionella, Ferrovum, Acidiphilium and Acidisphaera were almost absent. Ferrimicrobium (16.8%) and Sulfobacillus (1.4%) were detected in ShG14-1 but not in ShG14-8. Thus, the increase in concentration of metals in the acid mine drainage water under the same value of total acidity substantially altered the composition of the microbial community, preventing the development of “moderate” alpha- and beta-proteobacterial acidophiles, so that the community was dominated by the bacteria characteristic of the extremely acidic drainage waters.