School of Life Sciences, University of Warwick, Coventry CV4 7AL, UK.
Present address: Environment and Sustainability Institute, University of Exeter, Penryn Campus, Penryn, Cornwall, TR10 9FE, UK.
Microbiology (Reading). 2018 Mar;164(3):383-394. doi: 10.1099/mic.0.000616. Epub 2018 Feb 6.
The mineral sulfide-oxidising Acidithiobacillus ferrooxidans has been extensively studied over many years but some fundamental aspects of its metabolism remain uncertain, particularly with regard to its anaerobic oxidation of sulfur. This label-free, liquid chromatography-electron spray ionisation-mass spectrometry-based proteomic analysis estimated relative protein abundance during aerobic and anaerobic growth of At. ferrooxidans. One of its two bc1 complexes, that encoded by the petII operon, was strongly implicated in anaerobic ferric iron-coupled sulfur oxidation, probably in conjunction with two cytochromes. These two cytochromes are homologs of the Cyc2 and Cyc1 proteins that are involved in ferrous iron oxidation. The previously undetected cytochromes apparently associated with anaerobic growth in At. ferrooxidans appear to be absent in many other ferrous iron-oxidising acidophiles that can also reduce ferric iron, which suggests a diversity in the ferric-iron-coupled sulfur oxidation pathways. For aerobic growth of At. ferrooxidans, this analysis was consistent with the generally accepted mechanism for its oxidation of ferrous iron. Unexpectedly, proteins encoded by the petI operon were not abundant and generally not detected in the proteomic analyses of cells grown aerobically on sulfur, although there was some expression of genes of the petI and petII operons in these cells.
多年来，矿物硫化物氧化嗜酸菌（Acidithiobacillus ferrooxidans）得到了广泛的研究，但它的一些新陈代谢基本方面仍然不确定，特别是关于其对硫的无氧氧化。这项无标记、基于液相色谱-电子喷雾电离-质谱的蛋白质组学分析估计了嗜酸菌在有氧和无氧生长过程中的相对蛋白质丰度。其两个 bc1 复合物之一，由 petII 操纵子编码，强烈暗示与两种细胞色素一起参与无氧亚铁耦合硫氧化。这两种细胞色素是参与亚铁氧化的 Cyc2 和 Cyc1 蛋白的同源物。以前未检测到的细胞色素显然与嗜酸菌的无氧生长有关，而在许多其他也能还原三价铁的亚铁氧化嗜酸菌中似乎不存在，这表明三价铁耦合硫氧化途径存在多样性。对于嗜酸菌的有氧生长，这项分析与普遍接受的亚铁氧化机制一致。出乎意料的是，petI 操纵子编码的蛋白质在有氧生长硫的细胞的蛋白质组学分析中并不丰富，通常也检测不到，尽管这些细胞中 petI 和 petII 操纵子的一些基因有表达。
