Research On The Diversity Of Bacterial Communities In Acid Mine Drainage And The Succession Of AMD Niche In Different Concentration Of Fe～(3+)

Bioleaching refers to the use of microorganisms to leach metals such as copper, zinc, uranium, nickel and cobalt from a sulphide mineral. The process involves solublization of metals of interest through a series of biological and chemical oxidations of compounds containing sulfur which is then followed by a metal recovery step. This technique produces less air pollution and damage to geological formations, but mining companies should be careful of pollution that may generate from 'acid mine drainage' (AMD) and contaminate the groundwater. It is known that reported that a wide range of heterotrophic and chemolithotrophic bacteria can be detected in the acid-leaching environments. The geochemical conditions of the acid mine drainage were highly variable from site-to-site and the community compositions reflected this change in geochemical conditions.This study presents bacterial population analyses of microbial communities inhabiting three sites of acid mine drainage (AMD) in Shen-bu copper mine, Gansu Province, China. And we compared the shift of AMDniche by Fe stress at different concentration from two sites of AMD system in Dexing copper mine, in Jiangxi Province, China.Amplified ribosomal DNA restriction analysis (ARDRA) was used to analyze bacterial population by amplifying 16S rRNA of microorganisms. A total of 39 operational taxonomic units (OTUs) of all three samples were obtained and sequenced from 384 clones. Sequence data and phylogenetic analysis showed that two dominant clones in sample JYC-1 represented 69．5% of the total clones affiliated with Acidithiobacillus ferrooxidans (γ-Proteobacteria), and the most dominant clones of JYC-2 and JYC-3 were affiliated with Caulobacter crescentus (α-Protebacteria). At the level of bacterial divisions, differences in the relative incidence of particular phylogenetic groups among three samples with discrepancy of physico-chemical characteristics indicated that physico-chemical characteristics had much effect on phylogenetic diversity. Also the correlation between the discrepancy of physico-chemical characteristics and the diversity of bacteria community in the three samples suggested that the biogeochemical properties, pH and concentration of soluble metal could be the key factors for controlling the structure of bacterial population. Furthermore, Ferroplasma was abundant in sample JYC-1．Most Archaea were related to two undefined groups of Thermoplasmatales division.The shift of AMD niche by ferric iron stress at different concentration was also analyzed by ARDRA. Our result showed that the cells' growth was influenced by the concentration of ferric iron. The concentration of ferric iron overtopped the value 1．4 g/L, the higher the concentration of Fe³⁺ was the more prohibitive was. But a spot of ferric iron (0．28 g/L), the growth of the cells was accelerated. Phylogenetic analyses of 16S rRNA sequences revealed that there was a remarkable discrepancy of dominant bacteria in different culture conditions. There was a competition between At.ferrooxidans and Leptospirillum-like microorganisms in culture conditions. Both these acidophiles can grow via the oxidation of ferrous iron, causing accumulation of ferric iron; however, selection of the Leptospirillum-like microorganisms can occur and is thought to be due to their greater tolerance to ferric iron. Ferric iron toxicity has been detected in batch and chemostat studies of ferrous iron oxidation by At. ferrooxidans and chemostat studies of Leptospirillum-like microorganisms. The microbial succession that we observed in the different culture conditions seems to match the molecular data available from Acid Mine Drainage (AMD) systems. The community is dominated by Leptospirillum at the most extreme conditions of lower pH and higher ferric iron concentration. Conversely, Acidithiobacillus are the main components at slightly higher pH and ferric iron concentration.Strain ZYX capable of degrading organic sulfur (dibenzothiophene) were isolated by enrichment techniques from the petroleum-contaminated soil collected from Zhong Yuan Oil Field. The strain ZYX was the main study object in this experiment. It was gram-positive, non-motile and obligate aerobe. This strain underwent rod-coccus morphological change, and formed yellow-pigment glossy circular colonies measuring 1．5 mm in diameter on average after incubation for 2d (day) on LB (Luria-Bertani) plates. Strain ZYX was found most relative with the genus of Arthrobacter. The main morphological, biochemical and physiological features of strain ZYX were according with that of Arthrobacter. Some factors such as initial pH, carbon source, nitrogen source and sulfur source affecting the growth of strain ZYX were also studied. The experimental results showed that the optimal initial pH for growth was about 7．0, and the optimal concentration of DBT for growth was 0．01 g·L^-1 . Additionally, the optimal carbon source and nitrogen source were glycerol and glutamine. The strain could utilize coal as the sole sulfur source.