Although dissimilatory iron reduction and secondary mineral formation by Shewanella oneidensis MR-1 have been widely recognized, questions remain about the effects of biogenic Fe(II) on the rate and extent of secondary mineral formation and the importance of biogenic Fe(II)-induced crystallization processes. In this study, we investigated the effects of different mutants of MR-1 on the bioreduction and mineralization of ferrihydrite. The results indicate that while the reduction rates of ferrihydrite by ΔmtrD, ΔmtrF, and ΔomcA are similar to that of the wild type (WT), the capacity to reduce ferrihydrite decreased dramatically in the mutants ΔcymA and ΔmtrA. The order for Fe(III) reduction by MR-1 WT and mutants was ranked as follows: WT ≈ ΔmtrD ≈ ΔmtrF > ΔomcA > ΔmtrC > ΔcymA > ΔmtrA. Secondary minerals of ferrihydrite were characterized using X-ray diffraction, Fourier transform infrared spectra, and scanning electron microscopy. The results show that goethite and hematite were the main secondary minerals formed during the first 2 days in all treatments, and then magnetite appeared in the WT, ΔmtrD, ΔmtrF and ΔomcA treatments, whereas magnetite began to appear from the sixth day onward in the ΔmtrC treatment. However, no magnetite was observed during the 6 days in the ΔmtrA and ΔcymA incubation treatments. The plausible electron transfer pathways of bioreduction and phase transformation were also verified using thermodynamic calculations of elementary reactions. This study clarified the importance of Fe(II) production in secondary mineral formation processes and highlighted the significance of biogenic Fe(II)-catalyzed crystallization. This information may, in turn, help us to better understand natural microbe–mineral interaction processes.

中文翻译：

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次生矿物形成对沙瓦氏假单胞菌MR-1还原水铁矿生产Fe（II）的依赖性

尽管人们已经广泛认识到沙瓦氏假单胞菌MR-1的异化铁还原和次生矿物质的形成，但有关生物成因的Fe（II）对次生矿物质形成的速率和程度的影响以及由生物成因的Fe（II）诱导的重要性仍然存在疑问结晶过程。在这项研究中，我们调查了MR-1的不同突变体对水铁矿的生物还原和矿化的影响。结果表明，虽然ΔmtrD，ΔmtrF和ΔomcA对亚铁水合物的还原速率与野生型（WT）相似，但突变体ΔcymA和ΔmtrA的还原亚铁水合物的能力却显着降低。。通过MR-1 WT和突变体的Fe（III）还原的顺序位列如下：WT≈Δ mtrD ≈Δ MTRF >Δ OMCA >Δ地铁>Δ CYMA >Δ MTRA。使用X射线衍射，傅立叶变换红外光谱和扫描电子显微镜对亚铁酸盐的次生矿物进行表征。结果表明，针铁矿和赤铁矿是所有处理过程中最初两天形成的主要次生矿物，然后在WT，ΔmtrD，ΔmtrF和ΔomcA处理中出现磁铁矿，而从第六天起开始出现磁铁矿。在ΔmtrC中治疗。但是，在ΔmtrA和ΔcymA孵育处理的6天中未观察到磁铁矿。还使用基本反应的热力学计算验证了生物还原和相变的可能的电子转移途径。这项研究阐明了在次级矿物形成过程中生产Fe（II）的重要性，并强调了生物型Fe（II）催化结晶的重要性。这些信息反过来可以帮助我们更好地了解自然微生物与矿物质的相互作用过程。