Microbial community changes during the process of pyrite bioleaching

An analysis of the community composition of predefined mixed cultures (Acidithiobacillus ferrooxidans, Acidithiobacillus thiooxidans, Acidithiobacillus caldus, Leptospirillum ferrooxidans and Sulfobacillus thermosulfidooxidans) under different temperatures and initial pH values in pyrite bioleaching process was carried out. Denaturing gradient gel electrophoresis (DGGE) analysis of PCR-amplified 16S rDNA fragments from bacteria was used to evaluate the changes of the bacterial community in the process of pyrite bioleaching. Microbial community changes were observed in response to temperature and initial pH value changes. The species of predominant bacteria changed with the change of temperature at the same pH value. A. ferrooxidans and A. thiooxidans were the dominant species at 30°C and 35°C; L. ferrooxidans was also found at 35°C, while at 40°C it became the dominant species along with A. caldus and S. thermosulfidooxidans which was the dominant species both at 40°C and 45°C. The microbial community composition on the surface of pyrite was found to be similar with that in the bioleaching solution. It can be concluded that temperature had an important effect on the microbial community structure and composition in pyrite bioleaching.