再生水地下回灌过程中重金属抗性菌Citrobacter freundii JPG1 EPS与重金属铜运移的相互作用研究

发布时间：2018-10-24 10:47

【摘要】：再生水地下回灌是解决水资源短缺的一种有效途径。然而,经过处理的再生水中仍含有痕量的重金属,其穿过土壤和渗滤带引起地下水污染是一个受到关注的敏感问题。再生水地下回灌过程中重金属的迁移与截留受重金属的性质和浓度、渗滤层的水文条件、生物等多种因素影响。特别是当生物膜存在时,重金属在渗滤层中的迁移更加复杂。研究再生水地下回灌过程中重金属运移与生物膜胞外聚合物相互作用有助于揭示实际再生水地下回灌过程中铜的迁移和沉积规律,预测重金属对地下水的污染状况。为地下水重金属治理提供科学的理论依据,具有一定的理论指导意义。本文中以重金属铜抗性细菌Citrobacter freundii JPG1(Genbank accession KU513787)为对象,研究其对多种重金属的抗性。发现菌株JPG1对Cu~(2+)、Cd~(2+)、Ni~(2+)、Co~(2+)、Ag~+、Cr_2O_7~(2-)离子的MIC(Minimal Inhibitory Concentration,最小抑菌浓度)值分别为3、4、3、2、0.06、2 mM。重点研究了地下水中常见重金属Cu~(2+)离子对菌株JPG1生长的抑制作用。菌株JPG1具有较好的Cu~(2+)抗性,Cu~(2+)离子浓度小于0.25 mM基本不抑制其生长;Cu~(2+)离子浓度为1 mM时,对JPG1的抑制率约50%。在静态实验中,分别研究了菌株JPG1自身EPS(Extracellular Polymeric Substance,胞外聚合物)形成能力以及0.1mM铜对菌株JPG1-石英砂复合体EPS的影响。结果发现菌株JPG1的EPS形成能力较强,其EPS产量为118.82mg/g·VSS(mg/g·干重)。其中,蛋白和多糖含量分别为90.67、28.14 mg/g·VSS。0.1mM的Cu~(2+)离子作用影响了菌株JPG1-石英砂复合体EPS含量,使蛋白含量从491.67μg/g增加到700μg/g,而多糖含量维持在127-130μg/g。推测菌株JPG1可能是通过产生更多的胞外蛋白来抵抗Cu~(2+)离子的毒性作用。采用动态砂柱实验研究Cu~(2+)离子的运移和截留与菌株JPG1-石英砂复合体EPS形成间的相互作用。结果发现生物膜的形成导致了菌株JPG1-石英砂复合体孔隙的堵塞,使渗透系数低于初始时的10%。对于0.1 mM Cu~(2+)而言,菌株JPG1-石英砂复合体EPS的形成能将绝大部分的Cu~(2+)离子截留在砂柱中,出水中最大Cu~(2+)离子浓度仅为进水的3.05%。Cu~(2+)离子自下而上的穿透过有生物膜附着的石英砂柱后,首先抑制底层生物膜EPS的含量,使其EPS产量减少了原来的36.86%。Cu~(2+)离子渗透进砂层内部,使第二层到第五层中EPS分泌受到刺激,增加了原来的63%-141%。总之,菌株JPG1-石英砂复合体的EPS对回灌中的Cu~(2+)离子起到良好的截留作用。同时,Cu~(2+)离子的运移在一定程度上也刺激菌株JPG1-石英砂复合体EPS的分泌,二者表现为相互促进的作用。
[Abstract]:Reclaimed groundwater recharge is an effective way to solve the shortage of water resources. However, the treated recycled water still contains trace heavy metals, and the contamination of groundwater through soil and leachate is a sensitive problem. The migration and interception of heavy metals in reclaimed water are affected by the properties and concentrations of heavy metals, the hydrological conditions of leachate, biology and other factors. Especially when biofilm exists, the migration of heavy metals in percolation is more complicated. The study of the interaction between heavy metal migration and biofilm extracellular polymer during underground recharge of reclaimed water is helpful to reveal the migration and deposition of copper in the process of underground recharge of reclaimed water and to predict the pollution of groundwater caused by heavy metals. To provide a scientific theoretical basis for the treatment of heavy metals in groundwater, which has a certain theoretical significance. The resistance of copper-resistant bacteria (Citrobacter freundii JPG1 (Genbank accession KU513787) to various heavy metals was studied in this paper. It was found that the MIC (Minimal Inhibitory Concentration, minimum inhibitory concentration (MEC) of JPG1 to Cu~ (2), Cd~ (2), Ni~ (2), Co~ (2), Ag~, Cr_2O_7~ (2-) ions were 3 ~ 4 ~ (3), 3 ~ (3) ~ 0. 06 ~ (2) mM., respectively. The inhibitory effects of Cu~ (2) ions on the growth of strain JPG1 in groundwater were studied. The strain JPG1 had good Cu~ (2) resistance, Cu~ (2) ion concentration less than 0.25 mM did not inhibit its growth, and when Cu~ (2) ion concentration was 1 mM, the inhibition rate of JPG1 was about 50%. In the static experiment, the formation ability of EPS (Extracellular Polymeric Substance, extracellular polymer (EPS (Extracellular Polymeric Substance,) of strain JPG1 and the effect of 0.1mM copper on the EPS of JPG1- quartz sand complex were studied. The results showed that the EPS formation ability of strain JPG1 was strong, and its EPS yield was 118.82mg/g VSS (mg/g dry weight). The effect of Cu~ (2) on the content of protein and polysaccharide in the quartzite complex of the strain JPG1- was influenced by the action of Cu~ (2) with the content of 90.67c28.14 mg/g VSS.0.1mM, which increased the content of protein from 491.67 渭 g / g to 700 渭 g / g, while the content of polysaccharide was maintained at 127-130 渭 g / g. It is speculated that the strain JPG1 may resist the toxicity of Cu~ (2) ion by producing more extracellular proteins. The interaction between the migration and retention of Cu~ (2) ions and the formation of EPS of strain JPG1- quartz sand complex was studied by dynamic sand column experiment. The results showed that the formation of biofilm resulted in the pore blockage of the quartz sand complex of strain JPG1-, and the permeability coefficient was lower than that at the beginning. For 0. 1 mM Cu~ (2), the formation of strain JPG1- quartz sand complex EPS can intercept most of Cu~ (2) ions in the sand column. The maximum concentration of Cu~ (2) ion in the effluent was only 3.05. Cu2 ions from the bottom to the top of the quartz sand column with biofilm attached, and the content of EPS in the bottom biofilm was inhibited firstly. The EPS production decreased the original 36.86. Cu2 ion penetration into the sand layer, stimulated the secretion of EPS from the second layer to the fifth layer, increased the original 63-141. In conclusion, the EPS of the JPG1- quartz sand complex had a good retention effect on the Cu~ (2) ion in the recharge. At the same time, the migration of Cu~ (2) ions also stimulated the secretion of EPS from JPG1- quartz sand complex to a certain extent.
【学位授予单位】：东北师范大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：X703;X523

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