The Responses Of The Oxidation Of Ammonium In Soil And N. Europaea To Heavy Metals

In recent years, with unduly use of pesticides and fertilizers, as well as the rapid development of manufacturing, mining, industry, various forms of heavy metals into the atmosphere, water, soil, causing environmental pollution. The heavy metals have serious negative effects on soil organism and soil microbes after these heavy metal contaminants into the soil. Nitrification plays an important role in the nitrogen cycle, and nitrification is very sensitive to heavy metal stress, because it is the one of the most sensitive process to heavy metals. The results show that the heavy metals have the negative effect to microbial community structure,microbial biomass,basal respiration,mineralization of nutrients,CO2 metabolic quotient,soil enzyme activities. And it has been widely accepted that the high concentrations of heavy metals have serious negative impact on microorganism.This thesis regards the fluvo-aquic soil soil as the subject investigated, to study the response of potential nitrification rate in fluvo-aquic soil soil to heavy metals. Simultaneously, we analysis the amount changes and the changes of concentration enrichment site of heavy metals in N. europaea (ACTT 19718) utilizing the Ultra-thin sectioning technique,Transmission electron microscopy and Energy dispersive X-ray spectrometry.With increasing the concentration of heavy metal Zn2+, Ni2+, PNR was significantly decreased (p<0.01), When the concentration of Cd2+(1 mg·kg-1～10 mg·kg-1) is low, the PNR (Pontential Nitrification Rate) of the fluvo-aquic soil soil are significantly higher than the control group (p<0.05); When Cd2+concentration is higher than 10 mg·kg-1, PNR with the fluvo-aquic soil soil was significantly lower (p <0.01). When the concentration of Cu2+, Pb2+(0 mg·kg-1～1500 mg·kg-1) is low, the PNR do not differ from the control group. As the concentration of Fe2+(0 mg·kg-1 1500 mg·kg-1),Hg2+(0 mg·kg-1～2000 mg·kg-1),As2+(0 mg·kg¨1～20mg·kg-1),Cr2+(0 mg·kg-1～600mg·kg-1),Mn2+(0 mg·kg-1～3000mg·kg-1), the PNR do not differ from the control group. From EC50 values, inhibition on the degree of soil PNR is Pb <Cu< Ni<Zn< Cd.Although different treatments of heavy metals, European Nitrosomonas bacteria experience subtle differences because of the different culture conditions, showing the oval shape, the cell smooth surface and the complete cell wall. There is no difference between control group and the group treated by Zn2+. However, it is clear that there is black polymer body in the bacterial cells in the group treated by Cd2+. There is no different between the control group and the group treated by Zn2+in the content of C. By EDX analysis the Zn2+element is not found in the group treated by Zn2+, indicating that Zn element does not enter into the European Nitrosomonas bacterial cell. However, by the spectrum analysis of the group treaded by Cd2+, the black polymer contains a large amount of Cd elements, indicating that Cd2+in the European Nitrosomonas bacteria form a 80～100 nm size of the black block, and form a non-specific heavy metal complexes.N. europaea (ACTT 19718) contains the 16 kinds of amino acids including Asp, Thr, Ser, Glu, Gly, Ala, Cys, Val, Met, Iso, Leu, Tyr, Phe, His, Arg, Lys. The control group and the heavy metals treated group is the same of the types of amino acids, but the contents of amino are quite different. When the concentration of Cd2+is 0.02g·L-1, Asp, Thr, Ser, Gly, Val, Tyr significantly increase compared with the contro group (p<0.01), But when the heavy metal concentration of Cd2+arrives 0.04 g·L"1, the contents of these amino acids decrease with the heavy metal content increaseing.When the concentration of Zn2+is 0.05g·L-1, Asp, Thr, Ser, Leu significantly increase compared with the control group (p<0.01), But when the heavy metal concentration of Zn2+arrives 0.5 g·L-1, the contents of these amino acids decrease with the heavy metal content increaseing. However, the contents of some other amino acids such as Gly, Ala, Cys, Met, Iso, Tyr, Phe, His, Arg significantly decrease as the heavy metal content increase (p<0.01).In this study, we study the respond of the ammonia oxidizing bacteria to heavy metals, and we choose the sensitive type and concentration of heavy metals. Contemporary, using ultra-thin section technique, transmission electron microscopy (TEM) and energy dispersive X-ray spectrometry (EDS) associated use technology; we clarify how the heavy metal Zn2+ and Cd2+ enter into N. europaea (ACTT 19718) cell at the cellular level.