Salas Everett C, Berelson William M, Hammond Douglas E, Kampf Anthony R, Nealson Kenneth H
University of Southern California, Department of Earth Sciences.
Geochim Cosmochim Acta. 2010 Jan 15;74(2):574-583. doi: 10.1016/j.gca.2009.10.039.
Three bacterial strains from the genus Shewanella were used to examine the influence of specific bacteria on the products of dissimilatory iron reduction. Strains CN32, MR-4 and W3-18-1 were incubated with HFO (hydrous ferric oxide) as the terminal electron acceptor and lactate as the organic carbon and energy source. Mineral products of iron reduction were analyzed using X-ray powder diffraction, electron microscopy, coulometry and susceptometry. Under identical nutrient loadings, iron reduction rates for strains CN32 and W3-18-1 were similar, and about twice as fast as MR-4. Qualitative and quantitative assessment of mineralized end products (secondary minerals) indicated that different products were formed during experiments with similar reduction rates but different strains (CN32 and W3-18-1), and similar products were formed during experiments with different iron reduction rates and different strains (CN32 and MR-4). The major product of iron reduction by strains CN32 and MR-4 was magnetite, while for W3-18-1 it was a mixture of magnetite and iron carbonate hydroxide hydrate (green rust), a precursor to fougerite. Another notable difference was that strains CN32 and MR-4 converted all of the starting ferric iron material into magnetite, while W3-18-1 did not convert most of the Fe(3+) into a recognizable crystalline material. Biofilm formation is more robust in W3-18-1 than in the other two strains used in this study. The differences in mineralization may be an indicator that EPS (or another cellular product from W3-18-1) may interfere with the crystallization of magnetite or facilitate formation of green rust. These results suggest that the relative abundance of mineral end products and the relative distribution of these products are strongly dependent on the bacterial species or strain catalyzing iron reduction.
使用来自希瓦氏菌属的三株细菌来研究特定细菌对异化铁还原产物的影响。将菌株CN32、MR-4和W3-18-1与水合氧化铁（HFO）一起培养，以其作为末端电子受体，并以乳酸作为有机碳源和能源。使用X射线粉末衍射、电子显微镜、库仑法和磁测量法分析铁还原的矿物产物。在相同的养分负荷下，菌株CN32和W3-18-1的铁还原速率相似，约为MR-4的两倍。对矿化终产物（次生矿物）的定性和定量评估表明，在还原速率相似但菌株不同（CN32和W3-18-1）的实验中形成了不同的产物，而在铁还原速率不同且菌株不同（CN32和MR-4）的实验中形成了相似的产物。菌株CN32和MR-4还原铁的主要产物是磁铁矿，而对于W3-18-1来说，它是磁铁矿和碳酸氢氧化铁水合物（绿锈，是富铁蒙脱石的前体）的混合物。另一个显著差异是，菌株CN32和MR-4将所有起始的三价铁物质都转化为了磁铁矿，而W3-18-1并没有将大部分Fe(3+)转化为可识别的晶体物质。W3-18-1中的生物膜形成比本研究中使用的其他两株菌株更强。矿化的差异可能表明，胞外聚合物（或W3-18-1的另一种细胞产物）可能会干扰磁铁矿的结晶或促进绿锈的形成。这些结果表明，矿物终产物的相对丰度及其相对分布在很大程度上取决于催化铁还原的细菌种类或菌株。
