Extracellular Iron Biomineralization by Photoautotrophic Iron-Oxidizing Bacteria
Extracellular Iron Biomineralization by Photoautotrophic Iron-Oxidizing Bacteria
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DOI：
10.1128/aem.00490-09
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发表时间：
2009-09-01
影响因子：
4.4
通讯作者：
Morin, Guillaume
中科院分区：
文献类型：
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作者：
Miot, Jennyfer;Benzerara, Karim;Morin, Guillaume
光合厌氧铁氧化细菌Rhodobacter sp.菌株SW 2在中性pH下的铁氧化导致富铁矿物的形成。这些矿物质主要由纳米针铁矿（α-FeOOH）组成，其仅沉淀在细胞外，主要沉淀在从细胞中出现的聚合物纤维上。扫描透射X-射线显微镜分析表明，这些纤维是由脂质和多糖或脂多糖的混合物。这些纤维的铁和有机碳含量在25 nm尺度下线性相关，除了它们的纹理外，这表明这些纤维作为矿物沉淀的模板，随后是有限的晶体生长。此外，我们证明了铁氧化态的梯度沿着矿化纤维在亚微米尺度。这些纤维上的铁矿物在细胞接触处含有较高比例的Fe（III），并且Fe（II）的比例在远离细胞处增加。总之，这些结果表明铁生物矿化的有机聚合物的原始作用，并提供了第一个证据，这些nonencrusting，铁氧化细菌周围的氧化还原梯度的存在。
Iron oxidation at neutral pH by the phototrophic anaerobic iron-oxidizing bacterium Rhodobacter sp. strain SW2 leads to the formation of iron-rich minerals. These minerals consist mainly of nano-goethite (alpha-FeOOH), which precipitates exclusively outside cells, mostly on polymer fibers emerging from the cells. Scanning transmission X-ray microscopy analyses performed at the C K-edge suggest that these fibers are composed of a mixture of lipids and polysaccharides or of lipopolysaccharides. The iron and the organic carbon contents of these fibers are linearly correlated at the 25-nm scale, which in addition to their texture suggests that these fibers act as a template for mineral precipitation, followed by limited crystal growth. Moreover, we evidence a gradient of the iron oxidation state along the mineralized fibers at the submicrometer scale. Fe minerals on these fibers contain a higher proportion of Fe(III) at cell contact, and the proportion of Fe(II) increases at a distance from the cells. All together, these results demonstrate the primordial role of organic polymers in iron biomineralization and provide first evidence for the existence of a redox gradient around these nonencrusting, Fe-oxidizing bacteria.