Gagen Emma J, Zaugg Julian, Tyson Gene W, Southam Gordon
School of Earth and Environmental Sciences, The University of Queensland, St. Lucia, QLD, Australia.
Australian Centre for Ecogenomics, School of Chemistry and Molecular Biosciences, The University of Queensland, St. Lucia, QLD, Australia.
Front Microbiol. 2019 Dec 20;10:2938. doi: 10.3389/fmicb.2019.02938. eCollection 2019.
In tropical iron ore regions, biologically mediated reduction of crystalline iron oxides drives ongoing iron cycling that contributes to the stability of surface duricrusts. This represents a biotechnological opportunity with respect to post-mining rehabilitation attempts, requiring re-formation of these duricrusts. However, cultivated dissimilatory iron reducing bacteria typically reduce crystalline iron oxides quite poorly. A glucose-fermenting microbial consortium capable of reducing at least 27 mmol/L goethite was enriched from an iron duricrust region. Metagenome analysis led to the recovery of a metagenome assembled genome (MAG) of an iron reducer belonging to the alphaproteobacterial genus . This is the first report of iron reduction within the and the first reported genome of an iron-reducing, neutrophilic member of the Alphaproteobacteria. The MAG encodes putative metal transfer reductases (MtrA, MtrB) and a novel, multi-heme outer membrane cytochrome for extracellular electron transfer. In the presence of goethite, short chain fatty acid production shifted significantly in favor of acetate rather than propionate, indicating goethite is a hydrogen sink in the culture. Therefore, the presence of fermentative bacteria likely promotes iron reduction via hydrogen production. Stimulating microbial fermentation has potential to drive reduction of crystalline iron oxides, the rate limiting step for iron duricrust re-formation.
在热带铁矿石地区，生物介导的结晶氧化铁还原驱动着持续的铁循环，这有助于地表硬壳的稳定性。对于采后修复尝试而言，这代表了一个生物技术机会，因为需要重新形成这些硬壳。然而，培养的异化铁还原细菌通常对结晶氧化铁的还原能力很差。从一个铁硬壳区域富集到了一个能够还原至少27 mmol/L针铁矿的葡萄糖发酵微生物群落。宏基因组分析导致回收了一个属于α-变形杆菌属的铁还原菌的宏基因组组装基因组（MAG）。这是关于该属内铁还原的首次报道，也是首次报道的α-变形杆菌中铁还原嗜中性成员的基因组。该MAG编码推定的金属转移还原酶（MtrA、MtrB）和一种用于细胞外电子转移的新型多血红素外膜细胞色素。在针铁矿存在的情况下，短链脂肪酸的产生显著转向有利于乙酸盐而非丙酸盐，这表明针铁矿是培养物中的氢汇。因此，发酵细菌的存在可能通过产氢促进铁还原。刺激微生物发酵有可能推动结晶氧化铁的还原，这是铁硬壳重新形成的限速步骤。
