MECHANISM OF PESTICIDE BY SOIL ORGANIC MATTER

土壤有机质杀虫机理

• 批准号: 6120904
• 负责人: WILLIAM BLEAM
• 金额: $ 0.01万
• 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/6120904
• 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.

观察与自然风化的矿物相关的观察 地衣群落显示硅酸盐矿物风化反应 发生在复杂的微生物细胞外多糖凝胶中。 用斜长石进行矿物质溶解实验 Feldspar（CA0.75NA0.25AL1.75SI2.25O8）自然解决方案 发生多糖（4个藻酸盐，黄牙，果胶，淀粉） 具有类似于细胞外的结构和组成 由微生物产生的聚合物。 分析了解决方案 溶解的Si和Al作为长石溶解的指标。 在 中性pH，长石溶解被五个酸抑制 与有机自由对照相比，多糖。 但是， 未分化的藻酸盐显着增强了Si和Al 从Feldspar释放。 在酸性条件下，初始pH = 4，所有 与聚合物相比，聚合物增强了长石的溶解 无机控制。 果胶和牙龈黄质增加长石 溶解10倍，藻酸盐增强了长石 溶解为50至100。Si和Al浓度 即使解决方案是 相对于几个可能的二级阶段超饱和。 微生物细胞外聚合物影响矿物质的能力 风化反应不仅取决于功能的类型 组但也取决于这些配体的方向。 例如， 两个单体，包括藻酸盐，甘露环（M）和古鲁氏（G） 酸，将其羧基在赤道位置， 导致赤道位置1和4处的糖苷键 用于甘露酸酯和轴向沟。 多绿色酸盐形成a 平丝带，酸功能组远离 分子。 这种方向应允许在 顺序糖以键入矿物表面上的位置，甚至可能 抑制溶解。 多螺旋元形成一个弯曲的链（“鸡蛋盒） 结构”），羧基朝向分子。 该站点与溶液中的离子形成了双齿络合物。 我们会的 喜欢使用13C-NMR确定藻酸盐的结构 聚合物在我们的溶解实验中用于确定为什么它们 对矿物风化反应有不同的影响。 藻酸盐 富含GG块应与离子形成强大的复合物 解决方案，从而增强矿物风化。 我们也想 确定这些聚合物如何用金属离子（Al+3）形成复合物和 如果聚合物结构以复合物的形式变化。