MICROBIAL EXTRACELLULAR POLYMERS ON SILICATE MINERAL WEATHERING

微生物胞外聚合物对硅酸盐矿物风化的影响

• 批准号: 6298156
• 负责人: JILLIAN F BANFIELD
• 金额: $ 0.75万
• 依托单位: UNIVERSITY OF WISCONSIN-MADISON
• 依托单位国家: 美国
• 财政年份: 1999
• 资助国家: 美国
• 起止时间: 1999-03-01 至 2000-02-29
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6298156
• 关键词: bacteria; biological products; biomedical resource; carbohydrates; environmental health; nuclear magnetic resonance spectroscopy; plants

Observations of naturally weathered minerals associated with lichen communities show silicate mineral weathering reactions occurring in a complex microbial extracellular polysaccharide gel. Mineral dissolution experiments were performed with plagioclase feldspar (Ca0.75Na0.25Al1.75Si2.25O8) in solutions of naturally occurring polysaccharides (4 alginates, gum xanthan, pectin, starch) that have structures and compositions similar to extracellular polymers produced by microorganisms. Solutions were analyzed for dissolved Si and Al as an indicator of feldspar dissolution. At neutral pH, feldspar dissolution was inhibited by five of the acid polysaccharides compared to an organic free control. However, the undifferentiated alginate substantially enhanced both Si and Al release from the feldspar. Under acidic conditions, initial pH=4, all of the polymers enhanced feldspar dissolution compared to the inorganic controls. Pectin and gum xanthan increased feldspar dissolution by a factor of 10, and the alginates enhanced feldspar dissolution by a factor of 50 to 100. Si and Al concentrations continue to increase with time, even though solutions are super-saturated with respect to several possible secondary phases. The ability of microbial extracellular polymers to affect mineral weathering reactions depends not only on the types of functional groups but also on the orientation of these ligands. For example, the two monomers comprising alginate, mannuronic (M) and guluronic (G) acid, have their carboxylic groups in the equatorial position, resulting in glycosidic bonds at positions 1 and 4 that are equatorial for mannuronate and axial for guluronate. Poly-mannuronate forms a flat ribbon, with the acid functional group held out away from the molecule. This orientation should allow for the carboxyl groups in sequential sugars to bond to sites on mineral surfaces, and possibly inhibit dissolution. Poly-guluronate forms a buckled chain ("egg box structure"), with the carboxyl group oriented in towards the molecule. This site forms bidentate complexes with ions in solution. We would like to use 13C-NMR to determine the structure of the alginate polymers used in our dissolution experiments to determine why they have different effects on mineral weathering reactions. Alginates enriched in GG blocks should form strong complexes with ions in solution, thereby enhancing mineral weathering. We would also like to determine how these polymers form complexes with metal ions (Al+3) and if the polymer structures change as complexes form.

与自然风化矿物有关的观察 地衣群落显示硅酸盐矿物风化反应 出现在一种复杂的微生物胞外多糖凝胶中。 用斜长石进行了矿物溶解实验。 长石(Ca0.75Na0.25Al1.75Si2.25O8)在天然 富含多糖(4种海藻酸盐、黄原胶、果胶、淀粉) 它们的结构和成分类似于细胞外 由微生物产生的聚合物。对解决方案进行了分析 溶解的硅和铝作为长石溶解的指示剂。在… PH中性时，长石的溶解受到五种酸的抑制 将多糖与有机游离对照进行比较。然而， 未分化藻酸盐显著提高了硅和铝的含量 从长石中释放出来。在酸性条件下，初始pH=4，全部 聚合物对长石溶解的促进作用 无机对照。果胶和黄原胶增加长石 溶解10倍，海藻酸盐增强长石 以50到100倍的比例溶解。硅和铝的浓度 继续随时间增加，即使解决方案是 对于几个可能的第二阶段来说，是过饱和的。 微生物胞外聚合物对矿物质的影响能力 风化反应不仅取决于官能团的类型 这不仅取决于这些基团的取向，而且还取决于这些配体的取向。例如， 由海藻酸盐、甘露糖醛(M)和古龙酸(G)组成的两种单体 酸，使它们的羧基在赤道位置， 在1位和4位生成赤道糖苷键 用于甘露糖酸盐，轴用于古鲁酸盐类。聚甘露形成一种 扁平带状，酸性官能团远离 分子。这种取向应该允许中的羧基 顺序糖结合到矿物表面的位置，并可能 抑制溶解。聚古鲁酸形成了一条弯曲的链条(蛋盒 结构“)，其中羧基朝向分子。 该中心与溶液中的离子形成双齿络合物。我们会 我想用~(13)C-核磁共振来确定海藻酸盐的结构 我们在溶解实验中使用的聚合物，以确定它们为什么 对矿物风化反应有不同的影响。海藻酸盐 富含GG的嵌段应该与离子形成强烈的络合物 解决方案，从而加强矿物风化。我们也想要 确定这些聚合物如何与金属离子(Al+3)和 如果聚合物结构随着络合物的形成而改变。