| Mine tailings, caused by mining production activities, come rise to produce large numbers of mining waste land containing enormous amount of metal sulfides. Acid mine drainage (AMD) is formed by sulfide containing ore interacted with hydrosphere, atmosphere and microorganisms in supergene conditions. They are important source of mine environmental pollution. Although the mine tailings contain high concentration of sulfate and toxic metal ions, and the environment is extremely harsh, there still have large numbers of microorganisms exist here, forming an autotrophic biosphere in the subsurface stratum of ores. Through the microbial community structures and the distribution study of the mine tailings and the acid mine drainage, it can help us understand the impact factors of acidification process. Therefore, the study of metal sulfide oxidation microbes is of vital significance.Based on the acid mine drainage around the tailings wastelands and the allopelagic copper mine tailings under different vegetations in Tongling, our study tried to explore the relationship between the diversity and distribution of metal sulphide oxidation microorganisms in mine tailings with the vegetation, repairing phase and the depth of the tailings by using a16S rDNA-PCR, fluorescence quantitative PCR method. Our study showed that:(1) Phylogenetic analysis revealed that bacteria in the eight samples mainly fell into ten divisions, which were Betaproteobacteria, Gammaproteobacteria, Alphaproteobacteria, Deinococcus-Thermus, Nitrospira, Firmicutes, Actinobacteria, Deltaproteobacteria, Bacteroidetes, Chloroflexi. Archaea all fell into Thermoplasmatales order, tending to be thermophilic with three phylogenentic divisions, Thermoplasma, Ferroplasma and Thermogymnomonas. The UPGMA cluster analysis based on the microbial communities’ compositions revealed that five samples shared similarity in microbial community structure, with similarity degree ranging between66.98%and88.24%, which may resulted from the dominance of Meiothermus and Thermomonas. Two samples had the preponderant existence of iron-/sulfur-oxidizing bacterial (including Acidithiobacillus and Leptospirillum) with the total proportion up to86.11%and84.34%respectively. The remaining sample A owned higher microbial communities’ diversity, composed of iron/sulfur oxidization related bacteria, such as Acidithiobacillus, Leptospirillum, Sulfuricella, Thiobacillus and some heterotrophic bacteria, such as Herminiimonas, Polaromonas, Legionella, with the Shannon-Weaver H up to2.91, which may resulted from the less extreme surroundings.(2) Due to the low pH of AMD, the solubility of transition metals was greater and so AMD often typically contains elevated concentrations of metals, including iron, aluminium, manganese and other toxic transition metals whose present depending on the mineralogy of the host rock. Canonical Correlation Analysis (CCA) suggested that the dominance of Acidithiobacillus spp. had close relationship with the concentration of Fe3+, NO3-, SO42-and EC value. Leptospirillum spp. was significantly associated with the concentration of Cu2+and Fe3+. The distribution of Thermomonas and Meiothermus had no direct relation with the physical and chemical factors, which might caused by the comprehensive shaping of many factors.(3) Method of most probable number (MPN) was carried out to count the distribution of iron/sulfur-oxidization microorganisms in different depth of tailings in different repairing periods under different vegetation. The results showed that the amount of sulfur oxidizing bacteria gradually reduced with the increase of the depth of the tailings, which may be due to aerobic of sulfur bacteria. There was a stark contrast in the distribution of bacteria in tailings acidification harden layer, which might due to the sulfur oxidizing bacteria fond of acidic environment. Looking from the mine tailings under different repairing times, the content of sulfur oxidizing bacteria in soil-covered tailings was higher than tailings under other repairing phase. It showed that compared with tailings, the soil is more suitable for the growth of sulfur oxidizing bacteria. Looking from the different plants, the poison sumac and bamboo, owned with large roots, the sulfur oxidizing bacteria content was generally higher than that of other plants. It can be speculated that sulfur oxidizing bacteria growth dependent with the oxygen in the tailings, the tailings acidification, and the plant roots also has a certain relationship.(4) Realtime fluorescence quantitative PCR was carried out for the quantitative research of Acidithiobacillus ferrooxidans in mine tailings in different repair period under Imperata cylindrica communities. Our results showed that the quantity of A. ferrooxidans under early repairing period mine was lower than the later repairing mine under I. cylindrica communities, with the acidic of tailings reduced. It can be proved that I. cylindrica can effectively control further acidification of tailings. Due to the soil matrix is more suitable for the growth of bacteria, A. ferrooxidans existed more in the mine tailings covered with soil compared with the early and later repairing tailings, while the tailings under soil was far lower than the content of the bacteria in the repairing of early and later tailings.(5) The quantitative study of A. ferrooxidans based on the later repairing tailings of rhizosphere and non rhizosphere tailings under four different plants showed that the bacteria containing in the rhizosphere and non rhizosphere under I. cylindrica and Vetiveria zizanioides communities were less than Cynodon Rich and Miscanthussinensis Anderss, suggesting that I. cylindrica and V. zizanioides can effectively control the acidification of A. ferrooxidans. While naturally planted C. Rich and M. Anderss could grow in the high acidic tailings, with great difference between rhizosphere and non rhizosphere tailings. A. ferrooxidans existed in the non rhizosphere of C. Rich tailings is far higher than that of rhizosphere tailings, it seemed to be that C. Rich can shut out of the bacteria. In the contrary, bacteria content of rhizosphere of M. Anderss is much higher than the non rhizosphere tailings. A. ferrooxidans can be enriched near the rhizosphere tailings. The effect of plant rhizosphere on the distribution of microorganisms remains to be further research. |
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