Sani Rajesh K, Peyton Brent M, Dohnalkova Alice, Amonette James E
Department of Chemical Engineering, Center for Multiphase Environmental Research, Washington State University, Pullman, Washington 99164-2710, USA.
Environ Sci Technol. 2005 Apr 1;39(7):2059-66. doi: 10.1021/es0494297.
In cultures of Desulfovibrio desulfuricans 620 the effects of iron(III) (hydr)oxides (hematite, goethite, and ferrihydrite) on microbial reduction and reoxidation of uranium (U) were evaluated under lactate-limited sulfate-reducing conditions. With lactate present, G20 reduced U(VI) in both 1,4-piperazinediethanesulfonate (PIPES) and bicarbonate buffer. Once lactate was depleted, however, microbially reduced U served as an electron donor to reduce Fe(III) present in iron(III) (hydr)oxides. With the same initial amount of Fe(III) (10 mmol/L) for each iron(III) (hydr)oxide, reoxidation of U(IV) was greater with hematite than with goethite orferrihydrite. As the initial mass loading of hematite increased from 0 to 20 mmol of Fe(III)/L, the rate and extent of U(IV) reoxidation increased. Subsequent addition of hematite [15 mmol of Fe(III)/L] to stationary-phase cultures containing microbially reduced U(IV) also resulted in rapid reoxidation to U(VI). Analysis by U L3-edge X-ray absorption near-edge spectroscopy (XANES) of microbially reduced U particles yielded spectra similar to that of natural uraninite. Observations by high-resolution transmission electron microscopy, selected area electron diffraction, and energy-dispersive X-ray spectroscopic analysis confirmed that precipitated U associated with cells was uraninite with particle diameters of 3-5 nm. By the same techniques, iron sulfide precipitates were found to have a variable Fe and S stoichiometry and were not associated with cells.
在脱硫弧菌620的培养物中，研究了在乳酸盐受限的硫酸盐还原条件下，铁（III）（氢）氧化物（赤铁矿、针铁矿和水铁矿）对铀（U）微生物还原和再氧化的影响。存在乳酸盐时，G20在1,4 - 哌嗪二乙磺酸（PIPES）和碳酸氢盐缓冲液中均能还原U（VI）。然而，一旦乳酸盐耗尽，微生物还原的U就作为电子供体来还原铁（III）（氢）氧化物中存在的Fe（III）。对于每种铁（III）（氢）氧化物，初始Fe（III）量相同（10 mmol/L）时，赤铁矿对U（IV）的再氧化作用比针铁矿或水铁矿更强。随着赤铁矿的初始质量负载从0增加到20 mmol Fe（III）/L，U（IV）再氧化的速率和程度都增加。随后向含有微生物还原的U（IV）的稳定期培养物中添加赤铁矿[15 mmol Fe（III）/L]，也导致U（IV）迅速再氧化为U（VI）。通过U L3边缘X射线吸收近边光谱（XANES）对微生物还原的U颗粒进行分析，得到的光谱与天然晶质铀矿相似。高分辨率透射电子显微镜、选区电子衍射和能量色散X射线光谱分析观察结果证实，与细胞相关的沉淀U是粒径为3 - 5 nm的晶质铀矿。通过相同技术发现，硫化铁沉淀的Fe和S化学计量比可变，且与细胞无关。
