重金属镉对铜绿微囊藻的分层胞外聚合物淬灭机制研究

Study on Quenching Mechanism of the Layered Extracellular Polymer of Microcystis Aeruginosa by Heavy Metal Cadmium

通过三维荧光光谱法研究铜绿微囊藻(Microcystic aeruginosa)产毒株FACHB-905和不产毒株FACHB-469分层胞外聚合物(EPS)的差异性以及Cd(Ⅱ)对EPS的淬灭机制。结果表明:FACHB-905分层EPS中主要含有4种荧光基团(色氨酸、芳香蛋白Ⅰ和2种类腐殖酸),FACHB-469分层EPS中主要含有6种荧光基团(色氨酸、芳香蛋白Ⅰ和4种类腐殖酸)。两者的分层EPS中芳香类蛋白比色氨酸、类腐殖酸有更大的Cd(Ⅱ)结合能力,FACHB-469比FACHB-905更易与Cd(Ⅱ)结合,附着型LB/TB-EPS中芳香蛋白Ⅰ均能被Cd(Ⅱ)有效淬灭,且以动态淬灭为主导,类腐殖酸能被静态淬灭。Cd(Ⅱ)致使FACHB-469的TB-EPS中出现了类富里酸物质。两种铜绿微囊藻与Cd(Ⅱ)的反应都是自发的放热反应,氢键和范德华力在反应中起主要作用。

The difference of the extracellular polymeric substances(EPS)between two typical bloom cyanobacteria(Microcystis aeruginosa toxigenic FACHB-905 and non-toxigenic FACHB-469)was investigated and the quenching mechanism of the EPS by Cd(Ⅱ)was studied by three-dimensional fluorescence spectroscopy.The results show that there were four fluorescent groups(tryptophan,aromatic proteinⅠand two humic acids)and six fluorophores(tryptophan,aromatic proteinⅠand four humic acids)in the stratified EPS of FACHB-905 and FACHB-469 respectively.The latter two fluorophores have greater binding capacity with Cd(Ⅱ),and FACHB-469 is more likely to bind Cd(Ⅱ)than FACHB-905.The aromatic proteinⅠin LB/TB-EPS can be effectively quenched by Cd(Ⅱ)mainly in a dynamic way while the humic acid mainly in a static way.The fluorescence-producing fulvic acid appeared in TB-EPS of FACHB-469 after adding Cd(Ⅱ).The reactions of two species of Microcystis aeruginosa with Cd(Ⅱ)are to spontaneous exothermic reaction.In addition,hydrogen bond and van derWaals force play a major role in the reaction.