Ni Gaofeng, Simone Domenico, Palma Daniela, Broman Elias, Wu Xiaofen, Turner Stephanie, Dopson Mark
Centre for Ecology and Evolution in Microbial Model Systems (EEMiS), Linnaeus University, Kalmar, Sweden.
Front Microbiol. 2018 Dec 5;9:2945. doi: 10.3389/fmicb.2018.02945. eCollection 2018.
Mining and processing of metal sulfide ores produces waters containing metals and inorganic sulfur compounds such as tetrathionate and thiosulfate. If released untreated, these sulfur compounds can be oxidized to generate highly acidic wastewaters [termed 'acid mine drainage (AMD)'] that cause severe environmental pollution. One potential method to remediate mining wastewaters is the maturing biotechnology of 'microbial fuel cells' that offers the sustainable removal of acid generating inorganic sulfur compounds alongside producing an electrical current. Microbial fuel cells exploit the ability of bacterial cells to transfer electrons to a mineral as the terminal electron acceptor during anaerobic respiration by replacing the mineral with a solid anode. In consequence, by substituting natural minerals with electrodes, microbial fuel cells also provide an excellent platform to understand environmental microbe-mineral interactions that are fundamental to element cycling. Previously, tetrathionate degradation coupled to the generation of an electrical current has been demonstrated and here we report a metagenomic and metatranscriptomic analysis of the microbial community. Reconstruction of inorganic sulfur compound metabolism suggested the substrate tetrathionate was metabolized by the -like and -like populations via multiple pathways. Characterized species do not utilize inorganic sulfur compounds, suggesting a novel -like population had been selected. Oxidation of intermediate sulfide, sulfur, thiosulfate, and adenylyl-sulfate released electrons and the extracellular electron transfer to the anode was suggested to be dominated by candidate soluble electron shuttles produced by the -like population. However, as the soluble electron shuttle compounds also have alternative functions within the cell, it cannot be ruled out that acidophiles use novel, uncharacterized mechanisms to mediate extracellular electron transfer. Several populations within the community were suggested to metabolize intermediate inorganic sulfur compounds by multiple pathways, which highlights the potential for mutualistic or symbiotic relationships. This study provided the genetic base for acidophilic microbial fuel cells utilized for the remediation of inorganic sulfur compounds from AMD.
金属硫化物矿石的开采和加工会产生含有金属和无机硫化合物（如连四硫酸盐和硫代硫酸盐）的废水。如果未经处理就排放，这些硫化合物会被氧化，产生高酸性废水（称为“酸性矿山排水（AMD）”），造成严重的环境污染。一种修复矿山废水的潜在方法是“微生物燃料电池”这种不断发展的生物技术，它能够在产生电流的同时，可持续地去除产生酸性的无机硫化合物。微生物燃料电池利用细菌细胞在厌氧呼吸过程中将电子转移到矿物质作为终端电子受体的能力，通过用固体阳极取代矿物质来实现。因此，通过用电极取代天然矿物质，微生物燃料电池还提供了一个极好的平台，用于理解对元素循环至关重要的环境微生物与矿物质之间的相互作用。此前，已证明连四硫酸盐降解与电流产生相关，在此我们报告了对微生物群落的宏基因组和宏转录组分析。无机硫化合物代谢的重建表明，底物连四硫酸盐通过类似 和类似 的菌群经多种途径代谢。已鉴定的 物种不利用无机硫化合物，这表明选择了一种新的类似 的菌群。中间硫化物、硫、硫代硫酸盐和腺苷酰硫酸盐的氧化释放出电子，并且细胞外电子向阳极的转移被认为主要由类似 菌群产生的候选可溶性电子穿梭体主导。然而，由于可溶性电子穿梭体化合物在细胞内也有其他功能，不能排除嗜酸菌使用新的、未表征的机制来介导细胞外电子转移。群落中的几个菌群被认为通过多种途径代谢中间无机硫化合物，这突出了互利或共生关系的潜力。本研究为用于修复酸性矿山排水中无机硫化合物的嗜酸微生物燃料电池提供了遗传基础。
