U(VI) Reduction by Diverse Outer Surface c-Type Cytochromes of Geobacter sulfurreducens
U(VI) Reduction by Diverse Outer Surface c-Type Cytochromes of Geobacter sulfurreducens
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DOI：
10.1128/aem.02551-13
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发表时间：
2013-10-01
影响因子：
4.4
通讯作者：
Lovley, Derek R.
中科院分区：
文献类型：
--
作者：
Orellana, Roberto;Leavitt, Janet J.;Lovley, Derek R.
早期的研究表明，外表面的c型细胞色素可能在U（VI）还原中发挥作用，但最近有人提出，在被称为微生物纳米线的导电皮利表面有大量的U（VI）还原。对这一现象进行了进一步研究。一株G.硫还原菌，称为Aro-5，其产生的皮利的电导率大大降低，几乎与野生型一样，其中PilA（结构性菌毛蛋白）的基因被删除。为了将U（VI）还原率降低到野生型的20%以下，有必要删除G.硫还原菌X射线吸收近边结构光谱表明，与野生型细胞相关的83% +/- 10%的铀在孵育4小时后对应于U（IV），而与五重突变体，89% +/- 10%的铀是U（VI）。透射电子显微镜和X-射线能量色散谱显示，野生型细胞没有沉淀铀沿着皮利，如先前报道的，但U（IV）沉淀在细胞外表面。这些发现与以前的研究结果一致，即G。硫还原菌需要外表面C-型细胞色素而不是皮利来还原可溶性细胞外电子受体。
Early studies with Geobacter sulfurreducens suggested that outer-surface c-type cytochromes might play a role in U(VI) reduction, but it has recently been suggested that there is substantial U(VI) reduction at the surface of the electrically conductive pili known as microbial nanowires. This phenomenon was further investigated. A strain of G. sulfurreducens, known as Aro-5, which produces pili with substantially reduced conductivity reduced U(VI) nearly as well as the wild type, as did a strain in which the gene for PilA, the structural pilin protein, was deleted. In order to reduce rates of U(VI) reduction to levels less than 20% of the wild-type rates, it was necessary to delete the genes for the five most abundant outer surface c-type cytochromes of G. sulfurreducens. X-ray absorption near-edge structure spectroscopy demonstrated that whereas 83% +/- 10% of the uranium associated with wild-type cells correspond to U(IV) after 4 h of incubation, with the quintuple mutant, 89% +/- 10% of uranium was U(VI). Transmission electron microscopy and X-ray energy dispersion spectroscopy revealed that wild-type cells did not precipitate uranium along pili as previously reported, but U(IV) was precipitated at the outer cell surface. These findings are consistent with those of previous studies, which have suggested that G. sulfurreducens requires outer-surface c-type cytochromes but not pili for the reduction of soluble extracellular electron acceptors.