Natural attenuation of heavy metals occurs via coupled microbial iron cycling and metal precipitation in creeks impacted by acid mine drainage (AMD). Here, we describe the isolation, characterization, and genomic sequencing of two iron-oxidizing bacteria (FeOB) species: Thiomonas ferrovorans FB-6 and Thiomonas metallidurans FB-Cd, isolated from slightly acidic (pH 6.3), Fe-rich, AMD-impacted creek sediments. These strains precipitated amorphous iron oxides, lepidocrocite, goethite, and magnetite or maghemite and grew at a pH optimum of 5.5. While Thiomonas spp. are known as mixotrophic sulfur oxidizers and As oxidizers, the FB strains oxidized Fe, which suggests they can efficiently remove Fe and other metals via coprecipitation. Previous evidence for Thiomonas sp. Fe oxidation is largely ambiguous, possibly because of difficulty demonstrating Fe oxidation in heterotrophic/mixotrophic organisms. Therefore, we also conducted a genomic analysis to identify genetic mechanisms of Fe oxidation, other metal transformations, and additional adaptations, comparing the two FB strain genomes with 12 other Thiomonas genomes. The FB strains fall within a relatively novel group of Thiomonas strains that includes another strain (b6) with solid evidence of Fe oxidation. Most Thiomonas isolates, including the FB strains, have the putative iron oxidation gene cyc2, but only the two FB strains possess the putative Fe oxidase genes mtoAB. The two FB strain genomes contain the highest numbers of strain-specific gene clusters, greatly increasing the known Thiomonas genetic potential. Our results revealed that the FB strains are two distinct novel species of Thiomonas with the genetic potential for bioremediation of AMD via iron oxidation.

中文翻译：

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受酸性矿山排水影响的溪流的混合营养型铁氧化硫属单氧菌

重金属的自然衰减是通过微生物铁循环和受酸性矿山排水（AMD）影响的小溪中的金属沉淀而发生的。在这里，我们描述了两种铁氧化细菌（FeOB）的分离，表征和基因组测序：费奥洛斯硫杆菌（Thiomonas ferrovorans）FB-6和金属硫脲硫杆菌（Thiomonas metallidurans）FB-Cd，从弱酸性（pH 6.3），富铁，AMD受影响的小河沉积物。这些菌株沉淀出无定形氧化铁，纤铁矿，针铁矿，磁铁矿或磁赤铁矿，并在最适pH为5.5时生长。而硫磺属。FB菌株氧化了Fe，被称为混合营养型硫氧化剂和As氧化剂，这表明它们可以通过共沉淀有效地去除Fe和其他金属。以前的证据硫杆菌属 Fe氧化在很大程度上是模棱两可的，这可能是因为难以证明异养/混合营养生物中的Fe氧化。因此，我们还进行了基因组分析，以鉴定铁氧化，其他金属转化和其他适应作用的遗传机制，并将两个FB菌株基因组与其他12个硫磺属基因组进行比较。FB菌株属于相对较新的硫门氏菌菌株组，其中包括另一种具有铁氧化证据的菌株（b6）。大多数硫杆菌属菌株，包括FB菌株，都有推定的铁氧化基因cyc2，但只有两个FB菌株具有推定的Fe氧化酶基因mtoAB。。这两个FB菌株基因组包含最多数量的菌株特异性基因簇，大大增加了已知的硫磺单胞菌的遗传潜力。我们的研究结果表明，FB菌株是两个不同的新型硫杆菌属，具有通过铁氧化生物修复AMD的遗传潜力。