记者近日从中科院水保所获悉，该所青年科研人员方临川结合宏观吸附实验和等温滴定微量热、X射线吸收精细结构等多种现代仪器分析技术，在分子水平上揭示了土壤中细菌分泌的胞外聚合物（EPS）与针铁矿的作用过程和机理。该研究对揭示土壤的本质，合理调节土壤生物活性，阐明细菌黏附、生物膜形成和功能机制以及污染物的迁移分布等具有重要的理论和实际意义。
据了解，在自然界土壤中，80%～90%的微生物黏附在各种矿物或矿物—有机物复合体表面，形成单个的微菌落或生物膜。在形成生物膜之前，细菌分泌的胞外聚合物首先在土壤固相表面形成“条件膜”，以调控细菌的黏附和迁移，进而影响生物膜的结构和功能。
方临川研究发现，细菌分泌的胞外聚合物组分中蛋白质、核酸等大分子物质中的含磷基团与针铁矿表面羟基配位形成内圈络合物，且吸附产物结构与体系pH有密切关联。低pH时（pH为3.0），磷酸基团仅有一个去质子化的含氧阴离子直接和针铁矿表面的FeOH1/2-基团结合形成单齿络合物；而在高pH时（pH为9.0），磷酸盐基团中有2个含氧阴离子和针铁矿表面的2个FeOH1/2-基团结合形成双齿络合物。同时，体系pH由低到高时（3.0～9.0），吸附产物构型由单基配位向双基配位过渡，从而揭示出体系pH通过影响溶液中EPS-P中磷酸根质子解离和缔合，为导致吸附产物构型变化的重要原因。
该结果表明，土壤中微生物与矿物相互作用的过程中可能存在某种分子识别机制，细菌分泌的胞外聚合物与针铁矿之间P-O-Fe键的形成对于细菌黏附和生物膜的形成具有重要调控作用。
相关成果日前发表在国际学术期刊《水研究》上。（来源：中国科学报 张行勇）作者：方临川等 来源：《水研究》 发布时间：2012-12-14 10:21:22
Reactions between bacterial exopolymers and goethite: A combined macroscopic and spectroscopic investigation
The adsorption to goethite of extracellular polymeric substances (EPS) isolated from Pseudomonas putida was investigated using batch adsorption experiments, electrophoretic mobility (EM) measurements, Fourier transform infrared (FTIR) spectroscopy, isothermal titration calorimetry (ITC) and X-ray absorption fine structure (XAFS) spectroscopy. The adsorption of EPS decreased the point of zero charge of goethite from 7.6 to 3.2, suggesting the formation of negatively charged inner-sphere surface complexes. The adsorption isotherms of EPS on goethite conformed to the Langmuir equation. The adsorption energy constant (K) of EPS on goethite was in the sequence of EPS phosphate-containing moieties > nitrogen-containing moieties > carbon-containing moieties, indicating those containing phosphate were the most strongly adsorbed. FTIR showed ligand exchange of phosphate groups of EPS with surface hydroxyls on goethite. Extended X-ray absorption fine structure (EXAFS) and X-ray absorption near edge structure (XANES) spectroscopy results further demonstrated phosphate groups of EPS can form monodentate inner-sphere complexes at lower pH 3.0, while form bidentate inner-sphere complexes at higher pH 9.0. The oxidation state of iron in goethite was not changed after the reaction with EPS at different pH values. The information obtained in this study is of fundamental significance for the understanding of the interaction mechanisms between bacteria and minerals in soil and aquatic environments.
作 者：Linchuan Fang, Yuanyuan Cao, Qiaoyun Huang, Sharon L. Walker, Peng Caia
期刊名称：
期卷页： 第卷 第期 页
学科领域：生命科学 » 微生物学 » 微生物生理与生物化学
添加人是否为作者: 否
原文链接：http://www.sciencedirect.com/science/article/pii/S0043135412005404
DOI： 10.1016/j.watres.2012.07.046