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: 6309159
• 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: 2000
• 资助国家: 美国
• 起止时间: 2000-04-15 至 2005-02-28
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6309159
• 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.

天然风化矿物的观测结果 地衣群落显示硅酸盐矿物风化反应 存在于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 发生多糖（4藻酸盐，黄原胶，果胶，淀粉） 其结构和组成与细胞外的 由微生物产生的聚合物。 分析溶液的 溶解的Si和Al作为长石溶解的指示剂。 在 中性pH时，长石的溶解受到五种酸的抑制 多糖与有机游离对照相比。 但 未分化藻酸盐显著提高Si和Al 释放出长石。 在酸性条件下，初始pH=4，所有 的聚合物增强长石溶解相比， 无机控制。 果胶和黄原胶增加长石 溶解了10倍，藻酸盐增强了长石 溶解系数为50至100。 Si和Al浓度 随着时间的推移，尽管解决方案 相对于几种可能的次级相过饱和。 微生物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， 基团，但也对这些配体的取向。 比如说 包含藻酸盐、甘露糖醛酸（M）和古洛糖醛酸（G）的两种单体， 酸，其羧基位于赤道位置， 导致在位置1和4处的糖苷键是平伏的 对于甘露糖醛酸和轴向对于古洛糖醛酸。 聚甘露糖醛酸盐形成a 平坦的带状物，其中酸官能团远离 分子。 这种取向应允许羧基以 顺序糖键合到矿物表面的网站， 抑制溶解。 聚古洛糖醛酸盐形成一个弯曲的链（“蛋盒 结构”），羧基朝向分子。 该位点与溶液中的离子形成双齿络合物。 我们 我喜欢用13 C-NMR来确定海藻酸盐的结构 在我们的溶解实验中使用的聚合物，以确定为什么他们 对矿物风化反应有不同的影响。 藻酸 在GG块中富集的应该与离子形成强络合物， 溶液，从而增强矿物风化。 我们还要 确定这些聚合物如何与金属离子（Al+3）形成络合物， 如果聚合物结构随着复合物的形成而改变。