Analysis Of Bacterial Population Structure In Three Bioleaching System By PCR-DGGE

Denaturing gradient gel electrophoresis (DGGE) has been widely applied for study microbial population structures recent years. In this paper, DGGE was used to analyze the bacterial population structure of three controlled bioleaching systems—Ieaching of nickel sulfide ore by shake-flask culture, leaching of copper sulfide ore by stirred-tank culture and by column culture. The relationship between bacterial population structure and leaching efficiency was also mentioned.To understand the bacterial population structure in the bioleaching systems, culture method was used to isolate the leaching bacterial strains and forty strains were obtained from a low-grade chalcopyrite bioleaching culture. The Fe2+oxidation rate of fourteen strains was determined, showing the highest Fe2+oxidation rate is 99.3%, whereas the lowest is only 9.3%. Furthermore, three strains with comparatively high Fe2+oxidation rate—YK8, YK12 and YK14 were selected and their copper leaching efficiency was determined. The results showed that strain YK12 has the highest copper leaching efficiency of 58.82%.16S rRNA gene phylogenetic analysis of eight strains with different Fe2+ oxidation rate showed their high level of sequence similarity (99%), suggesting this bioleaching system was dominated by Acidithiobacillus ferrooxidans.To study the bacterial population structure and its change in the bioleaching process, method of genomic DNA extraction, PCR amplifying and DGGE were optimized. Genomic DNA was extracted by kit after concentrated by step centrifugation. Touchdown PCR program was performed to amplify 16S rRNA gene high variable regions and DGGE was run at a constant voltage of 100V in the 30% to 50% vertical denaturant gradient gel for 9h.Bacterial population structure in three bioleaching systems (leaching of nickel sulfide ore by shake-flask cultures, copper sulfide ore by stirred-tank cultures and column cultures) were analyzed by DGGE. Six bands were obtained in the column bioleaching, and one band in stirred tank bioleaching, three bands in shake flask bioleaching. All bands were recovered, cloned and sequenced. Phylogenetic analysis showed all bands had a high level of sequence similarity with A. ferrooxidans. It was found that in the column bioleaching process, the A. ferrooxidans population structure is comparatively complex, and the change of the population structure in the bioleaching phases was observed. But its copper leaching efficiency was relatively low. In the stirred-tank and shake-flask bioleaching process, the A. ferrooxidans population structure was simple, but the two bioleaching process had a relatively high copper leaching efficiency. The higher growth yield could contribute for this.In a summary, bacterial population structure in three controlled bioleaching systems were studied by DGGE analysis. This will benefit to understand and optimize the bacterial population structure in bioleaching system and improve the leaching efficiency.