Studies On The Mechanism Of Microbial Accumulation Of Uranium

Microorganisms are the most widely distributed organisms on the earth,which have a significant influence on geochemical changes.A large number of domestic and foreign research on the sandstone type uranium deposits has shown that most formation of sandstone type uranium deposits are affected by the geochemical behavior of microorganism,organic matters and oil gas in the different degree.Sometimes organic matters and microorganisms play more important role in the process of uranium's mineralization.If we master the mechanism of uranium's enrichment by microorganism,it can give us a guide to biological prospecting,and can help us using microorganism to purify wastewater which containing uranium.This research has very important practical value.This article mainly explores the role of microorganisms in the process of uranium's mineralization,focusing on the species of microorganisms in Mengqiguer uranium deposit in Yili basin,the relationship between the microorganisms and the interaction of uranium deposit and microorganisms.Firstly,nine fresh samples in the Mengqiguer uranium deposit are anaerobic culture,and it is found no expected changes in the culture medium.In order to determine whether there are microorganisms in the samples,we observe microorganisms by DAPI staining method,and find that microorganisms exist in the nine samples,but the quantity is very small.P4711-2 has the maximum phosphor dots,while each field has only 15 phosphor dots.The number of phosphor dots in P4711-1 and P4711-5 are also relatively large.After an enrichment culture to the three sample by adding uranium in this process,we obtain some microorganisms,then we analyze them from the point of molecular biology and morphology.Their species are determined through measuring their sequence of 16srDNA,as well as identifying the colony morphology,individual morphology,gram staining,spore and flagella staining.Through identification,we can see that the microorganisms in drilling core samples is not a single,which include Bacillus,Alcaligenes,Pseudomonas,Clostridium,Desulfotomaculum spp,Peptococcus branch denitrification spp.A variety of microorganisms can grow well under the condition of high concentration of uranium,illustrating that microorganisms may be associated with uranium's mineralization.We get 5 kinds of microorganisms by separating and purifying of this samples.One of the 5 kinds of microorganisms is Diaphorobacter,the rest is all Pseudomonas.We analyze whether the microorganisms in Mengqiguer uranium deposit affected uranium's mineralization through measuring the energy spectrum of bacteria and precipitation changes of U(?)in solution.The result is that only P4711-2 detects the existence of uranium and P4711-1 does not,and the existence of uranium is not detected in the five superior microorganisms.Testing the samples sent to Beijing Ministry of Nuclear Industry,the content of U(VI)in solution shows no sign of decreasing.At the same time,we has carried a study on the resistance capability to uranium in the five superior microorganisms.We culture the five superior microorganisms in different mediums,individually containing 50 mg/L,75 mg/L or 100 mg/L uranium solution.It is found that even containing up to 100mg/L,these five bacteria can grow well,indicating that they have a strong resistance to uranium capacity.From a series of experiments,we can't get the convincing evidence that microorganisms in Mengqiguer uranium deposit in Yili basin directly involved in uranium's enrichment,in that the the number of microorganisms is too small to work.It is also possible that the microorganisms just play an indirect role in uranium's metallogenic.Although we don't get the intuitive evidence that the microorganisms participate in uranium's enrichment directly,we can not deny that microorganisms effects on uranium's mineralization because a variety of microorganisms can survived under the condition of high concentration of uranium which is a toxic metal.