| 其他摘要 | Interaction between microorganism and minerals is universal geological process, and microorganism is directly involved in material cycling in nature. Research on mechanism of microbial weathering of minerals has been widely conducted in a close connection with mineral material, microorganism and environmental issues. However, research on mechanism of mineral weathering is lack of understanding of micro-process of weathering, physiological and biochemical characteristics of microorganism during weathering at present. With the fast development of theory and technology of molecular biology, theory and methods of geochemistry have been integrated with those of microbiology and molecular biology to study the processes of weathering of minerals by microorganism. To study microbio-geochemical processes at the interface between microorganism and minerals and mechanism of its feedback in molecular level is one of most important research themes in the geochemistry of the earth’s surface.
In this study, Aspergillus niger, Penicillium sp., Bacillus mucilaginosus were selected from soil, phosphorus ore and calcite as the studying materials for research on microbial weathering of minerals. Microbial weathering is a process of low consumption of energy, low pollution, short process, and hence a short cut to resolve confliction between exploitation and utilization of phosphorite and eco-environment protection due to activation of unavailable phosphorus in soil. It is of significance for exploitation and utilization of resource and building heath eco-environment. Using ion chromatography, ICP-OES, XRD, SEM, TEM, 2-DE and MC-ICP-MS analysis and measurement of technology, the microbial weathering of minerals by microorganism has been experimentally studied, and some major conclusions have been reached as follows.
(1) During the weathering of phosphorite by A. niger, biological and physical breakage are the main types of mineral weathering. The processes of weathering by microorganisms include formation of bio-film by fungal cell and macromolecule organic mass, mechanical denudation and penetration by fungal hypha, chelating of calcium by organic acids, production of oxalic acid calcium enhancing weathering of phosphorite. Direct weathering process due to close touch of fungal cell to phosphorite was stronger than the indirect one, in which phosphorite rock was put in dialysis bag.
(2) During the weathering of phosphorite rock by B. mucilaginosus, bacterial cell and its extracellar polysaccharide secreted by B. mucilaginosus form bio-film. Mechanical breakage and denudation by organic mass were important factors of mineral weathering. Direct weathering process which bacterial cell directly touch phosphorite was stronger than the indirect one.
(3) Weathering of phosphorite rock by A. niger was stronger than that by B. mucilaginosus. When weathering of the phosphorite rock by fungi and bacteria, biological and physical weathering played a key role in mineral weathering, but there was not oxalic acid calcium produced in process by B. mucilaginosus.
(4) During the weathering of phosphorite rock by B. mucilaginosus, expression of bacterial cell proteins shows significant variation, which could ascribed to phosphorite rock weathering. After phosphorite was put in culture, physiological metabolism of bacteria was changed. It is concluded that bacteria adapted environmental change through different metabolism process, causing mineral weathering.
(5) Weathering of bias was traced by using strontium isotopes during weathering of mixing of apatite and calcite by A. niger and Penicillium sp.. When the mixed minerals was weathered by A. niger, at the previous stage of weathering, the culture pH value was lower and the calcite was weathered; At a middle and later stage, the culture pH value increased and apatite was weathered strongly. Weathering of apatite result in macromolecule organic mass secreted by fungi chelated calcium of apatite. As far as Penicillium sp. concerned, during the previous stage, apatite was weathered in short time. In whole procedure, Penicillium sp. had good characteristic of weathering to calcite, sharp bias to apatite. The difference was produced by two fungi during weathering of apatite and calcite, which can be due to biological characteristic and culture environment of fungi. So A. niger and Penicillium sp. had a choice to attack different minerals. |
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