Diversity Of Typical Microbial Function Groups In Acid Mine Environments In Shizishan Sulfide Mine, Tongling, Anhui Province And Identification And Characterization Of An Isolated Iron-reducing Strain NJU-T2

The diversity of typical microbial function groups in acid mine environments in Shizishan sulfide mine, Tongling, Anhui Province and identification and characterization of an iron-reducing strain NJU-T2 were studied in this paper. Through taking the tailings and acid mine drainage samples from acid mine environments and using the overlay technique with four selective media YE, Feo, FeSo and FeTo, typical microbial function groups were isolated. The 16S rRNA gene sequences were amplified from total genomic DNA of bacteria isolates, then sequenced and analyzed by MEGA 5.0. The phylogenetic tree analysis with 16S rDNA gene sequences of isolates showed that all of the isolates belong to Acidithiobacillus, Acidosphaera, Acidocella, Acidiphilium, and can be divided into four microbial function groups, including heterotrophic acidophiles, autotrophic acidophiles, moderately acidophilic iron-oxidizing bacteria and acidophilic iron-reducing bacteria. It’s very important for these microbial function groups to maintain the formation and development of the acid mine drainage. The autotrophic bacteria are the primary producer in acidic mine drainage. They could oxidize low valence sulfur in sulfide minerals to sulfate and ferrous iron to ferric iron, producing energy to fix carbon dioxide to organic matter, and producing substances such as growth factor for the growth of other microorganisms of the acid mine drainage. The function of heterotrophic acidophiles was the dissimilatory reduction of ferric iron and to create an oligotrophic environment. The acidophilic iron-reducing bacteria were related to the reduction of trivalent iron. Through the synergy of acidophilic iron-reducing bacteria and iron oxidizing bacteria, the dynamic balance between ferrous iron and ferric iron could be realized, which allowing the acid mine water into a relatively stable ecosystem.Strain NJU-T2, isolated from tailings in the Shizishan acid mine environments, was subjected to a taxonomic study using the polyphasic approach. Colonies were white, nearly round, neat edge, with the dry surface. Cells were rod-shaped, non-spore forming, Gram-negative, motile by gliding and bacterial size (length*width) was 1.0-3.0umx0.2-0.3μm, Strain NJU-T2 is aerobic bacterium. Strain NJU-T2 could grow at 0-3.5% salinity and the optimum growth concentration of NaCl was 0%. The pH range was 2.0-6.0, with the optimal pH at 2.5. The temperature range was 4℃-40℃, with the optimum temperature was 30℃. Strain NJU-T2 could grow in FeTo, Fe3TSB、Waksman medium, but could not grow in MA、NA、TSB、R2A、 Starky-Na2S2O3 media. Fexirubin pigment was not detected in strain NJU-T2 cells. Serum inulin and salicin could be utilized as the sole carbon source, but could not use glucose, sucrose, galactose, fructose, ribose, rhamnose, mannitol, mannose, sorbitol, maltose, xylose, lactose, etc. and could not utilize nitrate and nitrite, could not make the gelatin liquefied, non-amylase activity, non-urease activity. Phylogenetic analysis based on the 16S rRNA gene sequence showed that strain NJU-T2 belongs to the genus Acidithiobacillus, with Acidithiobacillus sp.SM-2, Acidithiobacillus thiooxidans strain WJSo (100% similarity) as its closest relatives.The characteristics of strain NJU-T2 were studied. It is found that NJU-T2 could reduce ferric iron under aerobic conditions with plate and liquid cultural tests. The optimum growth pH was at pH 2.5, optimum growth temperature was at 30℃ and optimum ferric iron concentration was at 10 mmol/1. The NJU-T2 reduced ferric to ferrous iron, which provided initial energy to ferrous-oxidizing bacteria and maintained the Fe recycle and stability of acid mine environments. Meanwhile, it is found that NJU-T2 could oxidize elemental sulfur. Vitriol was detected in the Fe3TSB liquid culture and pH lowered over time.