【作者】 康福星；

【导师】 龙健；

【作者基本信息】 贵州师范大学 ， 环境科学， 2009， 硕士

【摘要】 微生物细胞体所分泌的胞外聚合物（extracellular polymeric substance.EPS）在医药、制奶工业和环境废水处理等领域扮演着重要的角色。为了探讨微生物及其胞外聚合物与重金属之间的作用机理,本研究采用实验室模拟的方法逐级深入地解析了钙化微生物对重金属胁迫的生理响应、重金属诱导下微生物EPS性质变异和重金属与EPS结合机理3个层面的关系。研究结果表明,首先,钙离子的存在能够使Cd对藻细胞的毒害作用减小,并保护其避免受到进一步损害。并且重金属Cd对藻体胁迫压力的减小是由于钙化层的保护作用。其次,微量Cu诱导下Synechocystis sp.能够产生大量分子量分布范围在14,000Da以上,且由苯环类蛋白和可溶性微生物产物所构成的EPS;并且EPS腐殖质类物质并不是微生物细胞直接分泌的产物,而是细胞残体或EPS经历腐殖化过程后的残余物质。最后,针对重金属Cd与2种具有不同类型EPS类蛋白结合机理的研究表明,在Cd浓度低于1×10^-4 mol·L^-1、pH值为4的条件下,Cd对LB具有显著的猝灭效应;这种猝灭现象不仅与生色团的质子化效应有关,而且也与类蛋白与Cd结合位点的变化有关。同时,Cd与2种类蛋白物质三维光谱分析结果显示,LB内荧光生色团性质和结构相对单一;而TB类蛋白的性质、结构与LB相比更具有多样性的特点。pH值为10的条件下,LB和TB类蛋白荧光团的猝灭与2方面因素有关,一是与生成不产生荧光的EPS-Cd络合物有关,二是与分子之间的碰撞所导致的荧光猝灭有关。该研究不仅在针对EPS与重金属适时结合过程的技术工作上有理论创新,而且该研究结论还有助于理解在微生物参与作用下重金属污染水体的自净过程,同时也具有较高的实际应用价值。更多还原

【Abstract】 Extracellular polymeric substance（EPS） secreted by microorganism plays an important role in pharmacy,cultured milk and wastewater treatment in environment. In order to understand the combining mechanism between microorganism & its extracellular polymeric substance and heavy metals.the study uses a stimulating method in laboratory to gradually understand at large relationship of three aspects as follows:physiological response of microorganism to heavy metal stress,changing EPS property induced by heavy metal and the combining mechanism between EPS and heavy metals.The results show in the following.Firstly,existing Ca²⁺ can decrease stress of heavy metal Cd on algal cells,and protect cells from more damage,which can be attributed to protecting effect of calcification layers triggered by bio-calcification.Secondly,slight Cu can induce Synechocystis sp.to produce more protein-like and soluble microbial product-like EPS that is MW>14.000Da.And humus in EPS is not from secretion of microorganism.but decaying and decomposing microorganism is its source.Finally,the results about combining mechanism between heavy metal Cd and two EPSs show that an obvious quenching effect of LB triggered by Cd concentration less than 1×10^-4 mol·L^-1 can be observed at pH value 4.The phenomena that was quenched at lower pH value was not only related with the protonation effect of fluorophores.but also linked with the change of combining sites between Cd and protein-like.In addition.for the analysis of further three-dimensional fluorescence spectrum,fluorophores of protein-like in LB have character of singleness,whereas fluorophores of TB have a characteristic of diversity.At pH 10 quenching of fluorescence peaks of protein-like in LB and TB are resulted from two aspects,on the one hand,it was related with the production of EPS-Cd complex,and on the other hand it can be attributed to colliding quenching between fluorescence molecules.In the study.theoretical innovation on fluorescence titration is not only exhibited but also these conclusions will help us to understand the self-purification of water columns in heavy metals.更多还原