Banfield J F, Barker W W, Welch S A, Taunton A
Department of Geology and Geophysics, University of Wisconsin, Madison, Wisconsin, USA.
Proc Natl Acad Sci U S A. 1999 Mar 30;96(7):3404-11. doi: 10.1073/pnas.96.7.3404.
Microorganisms modify rates and mechanisms of chemical and physical weathering and clay growth, thus playing fundamental roles in soil and sediment formation. Because processes in soils are inherently complex and difficult to study, we employ a model based on the lichen-mineral system to identify the fundamental interactions. Fixed carbon released by the photosynthetic symbiont stimulates growth of fungi and other microorganisms. These microorganisms directly or indirectly induce mineral disaggregation, hydration, dissolution, and secondary mineral formation. Model polysaccharides were used to investigate direct mediation of mineral surface reactions by extracellular polymers. Polysaccharides can suppress or enhance rates of chemical weathering by up to three orders of magnitude, depending on the pH, mineral surface structure and composition, and organic functional groups. Mg, Mn, Fe, Al, and Si are redistributed into clays that strongly adsorb ions. Microbes contribute to dissolution of insoluble secondary phosphates, possibly via release of organic acids. These reactions significantly impact soil fertility. Below fungi-mineral interfaces, mineral surfaces are exposed to dissolved metabolic byproducts. Through this indirect process, microorganisms can accelerate mineral dissolution, leading to enhanced porosity and permeability and colonization by microbial communities.
微生物改变化学和物理风化以及黏土生长的速率和机制，因此在土壤和沉积物形成过程中发挥着重要作用。由于土壤中的过程本质上很复杂且难以研究，我们采用基于地衣 - 矿物系统的模型来确定基本的相互作用。光合共生体释放的固定碳刺激真菌和其他微生物的生长。这些微生物直接或间接诱导矿物解聚、水化、溶解以及次生矿物形成。使用模型多糖来研究细胞外聚合物对矿物表面反应的直接介导作用。多糖可使化学风化速率抑制或增强多达三个数量级，这取决于pH值、矿物表面结构和组成以及有机官能团。镁、锰、铁、铝和硅被重新分配到强烈吸附离子的黏土中。微生物可能通过释放有机酸促进不溶性次生磷酸盐的溶解。这些反应显著影响土壤肥力。在真菌 - 矿物界面以下，矿物表面会接触到溶解的代谢副产物。通过这个间接过程，微生物可以加速矿物溶解，从而导致孔隙率和渗透率增加以及微生物群落的定殖。
