The fungus Beauveria caledonica was highly tolerant to toxic metals and solubilized cadmium, copper, lead, and zinc minerals, converting them into oxalates. This fungus was found to overexcrete organic acids with strong metal-chelating properties (oxalic and citric acids), suggesting that a ligand-promoted mechanism was the main mechanism of mineral dissolution. Our data also suggested that oxalic acid was the main mineral-transforming agent. Cadmium, copper, and zinc oxalates were precipitated by the fungus in the local environment and also in association with the mycelium. The presence of toxic metal minerals often led to the formation of mycelial cords, and in the presence of copper-containing minerals, these cords exhibited enhanced excretion of oxalic acid, which resulted in considerable encrustation of the cords by copper oxalate hydrate (moolooite). It was found that B. caledonica hyphae and cords were covered by a thick hydrated mucilaginous sheath which provided a microenvironment for chemical reactions, crystal deposition, and growth. Cryo-scanning electron microscopy revealed that mycogenic metal oxalates overgrew parental fungal hyphae, leaving a labyrinth of fungal tunnels within the newly formed mineral matter. X-ray absorption spectroscopy revealed that oxygen ligands played a major role in metal coordination within the fungal biomass during the accumulation of mobilized toxic metals by B. caledonica mycelium; these ligands were carboxylic groups in copper phosphate-containing medium and phosphate groups in pyromorphite-containing medium.
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机译:球孢白僵菌真菌对有毒金属和可溶的镉,铜,铅和锌矿物质具有很高的耐受性,可将其转化为草酸盐。该真菌被发现过度排泄具有强金属螯合特性的有机酸(草酸和柠檬酸),这表明配体促进机制是矿物溶解的主要机制。我们的数据还表明草酸是主要的矿物转化剂。镉,铜和草酸锌在当地环境中以及与菌丝体一起被真菌沉淀。有毒金属矿物质的存在通常会导致菌丝的形成,而在含铜矿物质的存在下,这些绳索表现出草酸排泄量的增加,这会导致草酸盐铜水合物(软沸石)对绳索产生明显的结壳。人们发现,Caledonica孢菌的菌丝和脐带被厚厚的水合粘液鞘覆盖,这为化学反应,晶体沉积和生长提供了微环境。低温扫描电子显微镜显示,致癌性金属草酸盐使亲代真菌菌丝过度生长,在新形成的矿物质中留下了迷宫状的真菌通道。 X射线吸收光谱显示,氧合配体在Caledonica B. caledonica菌丝体迁移的有毒金属积累过程中,在真菌生物量内的金属配位中起主要作用。这些配体在含磷酸铜的介质中为羧基,在含焦亚硫酸盐的介质中为磷酸基。
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