Interactions between Bacillus mucilaginosus and silicate minerals (weathered adamellite and feldspar): Weathering rate, products, and reaction mechanisms

摘要

Bacillus mucilaginosus is a common soil bacterium, and usually used as a model bacterium in studying microbe-mineral interactions. Several reaction mechanisms of B. mucilaginosus weathering silicate minerals were proposed. However, the molecule mechanisms and detailed processes were still unclear. In this paper, bacteriummineral interactions were studied in terms of variations in pH value over the experimental period, variations in mineral composition, weathering rates of silicate minerals and volatile metabolites in the culture medium, etc., to further explore the bacterium-mineral interaction mechanisms. The results showed that B. mucilaginosus could enhance silicate mineral weathering obviously. The weathering rates were quite different for various kinds of silicate minerals, and the weathering rate of weathered adamellite could reach 150 mg/m2/d. Although B. mucilaginosus produced little acidic substance, pH in the microenvironment of bacterium-mineral complex might be far lower than that of the circumjacent environment; a large amount of acetic acid was found in the metabolites, and was likely to play an important role as a ligand. These results appear to suggest that acidolysis and ligand degradation are the main mechanisms of B. mucilaginosus dissolving silicate minerals, the formation of bacterium-mineral complexes is the necessary condition for the bacteria weathering silicate minerals, and extracelluar polysaccharides played important roles in bacterium-mineral interaction processes by forming bacterium-mineral complexes and maintaining the special physicochemical properties of microenvironment.