IMAR-CMA, 3004-517 Coimbra, Portugal.
Metallomics. 2013 Apr;5(4):390-7. doi: 10.1039/c3mt00052d.
Severe environmental problems arise from old uranium mines, which continue to discharge uranium (U) via acid mine drainage water, resulting in soil, subsoil and groundwater contamination. Bioremediation of U contaminated environments has been attempted, but most of the conceptual models propose U removal by cell suspensions of anaerobic bacteria. In this study, strain Rhodanobacter A2-61, isolated from Urgeiriça Mine, Portugal, was shown to resist up to 2 mM of U(vi). The conditions used (low nutrient content and pH 5) potentiated the interaction of the toxic uranyl ion with the tested strain. The strain was able to remove approximately 120 μM of U(vi) when grown aerobically in the presence of 500 μM U. Under these conditions, this strain was also able to lower the phosphate concentration in the medium and increased its capacity to take up inorganic phosphate, accumulating up to 0.52 μmol phosphate per optical density unit of the medium at 600 nm, after 24 hours, corresponding approximately to the late log phase of the bacterial culture. Microscopically dense intracellular structures with nanometer size were visible. The extent of U inside the cells was quantified by LS counting. EDS analysis of heated cells showed the presence of complexes composed of phosphate and uranium, suggesting the simultaneous precipitation of U and phosphate within the cells. XRD analysis of the cells containing the U-phosphate complexes suggested the presence of a meta-autunite-like mineral structure. SEM identified, in pyrolyzed cells, crystalline nanoparticles with shape in the tetragonal system characteristic of the meta-autunite-like mineral structures. U removal has been reported previously but mainly by cell suspensions and through release of phosphate. The innovative Rhodanobacter A2-61 can actively grow aerobically, in the presence of U, and can efficiently remove U(vi) from the environment, accumulating it in a structural form consistent with that of the mineral meta-autunite inside the cell, corresponding to effective metal immobilization. This work supports previous findings that U bioremediation could be achieved via the biomineralization of U(vi) in phosphate minerals.
从旧铀矿中产生了严重的环境问题，这些铀矿通过酸性矿山排水继续排放铀 (U)，导致土壤、底土和地下水受到污染。人们尝试过用生物修复来治理 U 污染的环境，但大多数概念模型都提出通过厌氧细菌的细胞悬浮液去除 U。在这项研究中，从葡萄牙 Urgeiriça 矿中分离出的 Rhodanobacter A2-61 菌株被证明能够抵抗高达 2mM 的 U(vi)。所使用的条件（低营养含量和 pH5）增强了有毒铀酰离子与测试菌株的相互作用。当该菌株在有氧条件下生长并在 500μM U 存在的情况下生长时，它能够去除大约 120μM 的 U(vi)。在这些条件下，该菌株还能够降低培养基中的磷酸盐浓度，并增加其吸收无机磷酸盐的能力，在 600nm 处的培养基光密度单位中积累高达 0.52μmol 磷酸盐，在 24 小时后，大约相当于细菌培养的对数后期。可以看到显微镜下致密的纳米级大小的细胞内结构。通过 LS 计数定量了细胞内 U 的含量。对加热细胞的 EDS 分析表明，存在由磷酸盐和铀组成的复合物，表明 U 和磷酸盐在细胞内同时沉淀。对含有 U-磷酸盐复合物的细胞的 XRD 分析表明，存在类似于钙铀云母的矿物结构。SEM 在热解细胞中识别出具有特征性四方系统形状的纳米级结晶纳米颗粒，这是类似于钙铀云母的矿物结构。先前已经报道了 U 的去除，但主要是通过细胞悬浮液和释放磷酸盐。创新的 Rhodanobacter A2-61 可以在有氧条件下，在 U 的存在下主动生长，并能有效地从环境中去除 U(vi)，将其积累在与细胞内钙铀云母相似的结构形式中，这对应于有效的金属固定。这项工作支持了先前的发现，即通过生物矿化将 U(vi)转化为磷酸盐矿物可以实现 U 的生物修复。
