Uranium contamination of soils and groundwater in the United States represents a significant health risk and will require multiple remediation approaches. Microbial phosphatase activity coupled to the addition of an organic P source has recently been studied as a remediation strategy that provides an extended release of inorganic P (Pi) into U-contaminated sites, resulting in the precipitation of meta-autunite minerals. Previous laboratory- and field-based biomineralization studies have investigated environments with relatively high U concentrations (>20 μM). However, most contaminated sites have much lower U concentrations (<2 μM). The Environmental Protection Agency (EPA) limit for U in drinking water is 0.126 μM. Reaching this regulatory limit becomes challenging as U concentrations approach autunite solubility. We studied the precipitation of U(VI)-phosphate minerals by an environmental isolate of Caulobacter sp. (strain OR37) from an Oak Ridge, Tennessee, U-contaminated site. Abiotic U(VI) solubility experiments reveal that U(VI)-phosphate minerals do not form in the presence of excess Pi (500 μM) when U(VI) concentrations are <1 μM and pH is <5. When OR37 cells are reacted under the same conditions with Pi or glycerol-2-phosphate, U(VI)-phosphate mineral formation was observed, along with the formation of intracellular polyphosphate granules. These results show that bacteria provide supersaturated microenvironments needed for U(VI)-phosphate mineralization while hydrolyzing organic P sources. This provides a pathway to lower U concentrations to below EPA limits for drinking water.

中文翻译：

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由铀的浓度和pH值对U型磷酸盐生物矿化的影响柄杆菌OR37

在美国，铀污染土壤和地下水代表着重大的健康风险，将需要采取多种补救措施。耦合到所述加入有机P源的微生物的磷酸酶活性，最近被研究作为一个补救策略，提供了无机P（PI）的延长释放到U形受污染场地，导致的析出元-铁矿物质。先前基于实验室和现场的生物矿化研究已经研究了U浓度相对较高（> 20μM）的环境。但是，大多数受污染的地点的U浓度要低得多（<2μM）。环境保护局（EPA）对饮用水中U的限量为0.126μM。随着U浓度接近金铁矿溶解度，达到此监管极限变得具有挑战性。我们研究了环孢细菌的环境分离物对U（VI）-磷酸盐矿物的沉淀sp。（菌株OR37）来自田纳西州橡树岭，受到U污染。非生物U（VI）溶解度实验表明，当U（VI）浓度<1μM和pH <5时，在过量的Pi（500μM）存在下不会形成U（VI）-磷酸盐矿物质。当OR37细胞在相同条件下与Pi或2-磷酸甘油酯反应时，观察到U（VI）-磷酸酯矿物质的形成，以及细胞内多磷酸盐颗粒的形成。这些结果表明，细菌提供了U（VI）-磷酸盐矿化所需的过饱和微环境，同时还水解了有机P源。这提供了将U浓度降低至EPA饮用水限值以下的途径。