Investigation On Soil Microorganism Community Distribution Of Uranium Mine In Ruoergai Area And Response To Exogenous Uranium Pollution Stress

Heavy metal pollution research has become the focus of environmental science. As the microbial living in the soil, it is more sensitive than plants and animals when suffer from the heavy metal stress. Once the heavy metal contaminated soil will inhibit the microbial growth and metabolism, lead to changes in the microbial community structure,seriously affect plant growth, damage the ecological balance of stability, thereby affecting human and animal health. However, the relationship between heavy metal contamination and microbial communities have been studied for many, while repeatedly by heavy metal pollution of the environment quality change has been ignored.Therefore,the study about heavy metal pollution stress on soil microbial community groups to explore the characteristics of microbial growth in the secondary distribution of soil pollution in the environment, as well as ecological quality evaluation of soil heavy metal stress has important scientific significance and application prospects.The soil samples were collected from different pollution sites in the Zoige uranium ore field to comprehensive survey of the distribution of micro-organisms in the study area; investigated four stress grades of the exogenous uranium pollution? 10, 50, 100,200 mg / kg? in soil samples to research the relationship between exogenous uranium stress and biological indicators of soil environmental quality; discussed the effects of exogenous uranium stress on soil microbial community structure by BIOLOG-ECO board; obtained the soil bacterial communities difference variation in the level of genus and species under the exogenous uranium stress by using Mi Seq sequencing technology.The results are as follows.1. In order to study the relationship between chemical speciation of heavy metals and microbial community distribution in mine, the soil samples were collected from different pollution sites along Zhongchang ditch, Yangchang ditch, Sulimutang in Zoige uranium mine. The soil microbial quantity and community were analyzed with dilution-plate method. The dominant strains from these plates were identified by using16 S r DNA sequence analysis method and Biolog automated microbial identification system. And the stress screening method was used to isolate microbe strains with hightolerance to U?VI?. The total number of microorganisms in the soil samples was similar to the normal soil, with bacteria?8.40×105- 2.50×108 CFU/g? > the actinomycetes?2.40×104- 1.76×106 CFU/g? > the fungi?1.00×102- 3.20×104 CFU/g?. The amount of three types of microorganisms with a decreasing trend was observed as the depth of soil increasing. The vertical direction in the soil, with the three main types of soil microbial quantity deepen the depth decreases, the depth of 20 cm in each sampling point average number of microorganisms decreased to about 30% of the surface. We have screened three pairs of bacteria which had a high resistance to the concentration of 120 mg / L of uranium from the study area.2. Research on the ecological response of soil microbial community metabolism of exogenous uranium stress by BIOLOG-ECO board. The results showed that the soil microbial activity decrease with the increase of concentration of exogenous uranium,the same as the Mc Intosh index. But it did not significantly affect Shannon index and Simpson index. The ability to utilize amino acids of microbial community was the highest, will phenolic acids was the lowest. Principal component analysis showed, soil microorganism in TY02 groups mainly impact of PC1 and PC2 which with a larger contribution of carbon, TY05 groups mainly impact of PC2 which with a larger contribution of carbon, and TY10 groups mainly impact of PC1 which with a larger contribution of carbon. The carbohydrate microbial communities made a great contribution to PC1 and PC2.3. Measured the changes of soil bacteria on genus under exogenous uranium stress by using Mi Sep high-throughput sequencing technology. 12 shared genus and 14 unique bacterias among TY02, TY05 and TY10?accounting for more than 1% each of the total number of bacteria? were found through OTU cluster analysis, but Gracilibacter and Lutispora only been found in TY05. According to the three treatment groups flora OTU analysis to identify three treatment groups after different exogenous uranium stress treatment, a total of dominant bacteria in each group, which was partially analysis of uranium has a strong resistance to bacteria such as Subgroup_6norank,Gaiellales_uncultured, RB41_norank, Actinobacteria_norank, Gaiella etc; partially uranium sensitive bacteria, such as Microlunatus, Bacillus, Ensifer etc; get somebacteria such as Oxalobacteraceae_unclassified, Paucimonas, Geobacter, etc., with exogenous uranium stress concentration increases, the number of bacteria increase.4. In this study, microbial biomass carbon, microbial biomass nitrogen, microbial quotient, metabolic quotient and soil enzyme activity were determined in the soil which were polluted by different stress concentrations of exogenous uranium pollution from the uranium mining area. The result showed that the main heavy metalel ements found in the polluted area were As, Cd and U. The increasing concentration of exogenous uranium pollution inhibited the microbial quantity, sucrase activity, catalase activitiy and urease activity to different extent. A significant positive correlation was shown to exist between exogenous uranium pollution and soil metabolic quotient whereas a negative correlation between exogenous uranium pollution and microbial biomass carbon, microbial biomass nitrogen as well as microbial quotient. These important biological indicators can express the evolution of the soil environmental quality under the exogenous heavy metal pollution. The number of Fungi reduced by 83%, 71%, 37%from the surface to the deep, the number of bacteria reduced by 42%, 24%, 28%, the number of actinomycetes reduced by 23%, 11%, 18%.The research showed that the total number of microorganisms in the soil samples was similar to the normal soil, and we have screened three pairs of bacteria which had a high resistance to the concentration of 120 mg/L of uranium from the study area. The ability to utilize amino acids of microbial community was the highest, will phenolic acids was the lowest, and the soil microbial activity decrease with the increase of concentration of exogenous uranium. 12 shared genus and 14 unique bacterias among TY02, TY05 and TY10?accounting for more than 1% each of the total number of bacteria? were found through OTU cluster analysis, but Gracilibacter and Lutispora only been found in TY05. The increasing concentration of exogenous uranium pollution inhibited the microbial quantity, sucrase activity, catalase activitiy and urease activity to different extent. A significant positive correlation was shown to exist between exogenous uranium pollution and soil metabolic quotient whereas a negative correlation between exogenous uranium pollution and microbial biomass carbon, microbial biomass nitrogen as well as microbial quotient. Expand research on the stress heavy metal pollution of soil microbial communities grouping feature, the search for microbialgrowth in the secondary distribution of soil pollution in the environment, as well as ecological quality evaluation of soil heavy metal stress has important scientific significance and application prospects.