Molecular Microbiology, Institute for Biology/Microbiology, Martin-Luther-University Halle-Wittenberg, Kurt-Mothes-Str. 3, 06120 Halle (Saale), Germany.
Metallomics. 2018 Feb 21;10(2):278-286. doi: 10.1039/c7mt00312a.
The bacterium Cupriavidus metallidurans is capable of reducing toxic Au(i/iii)-complexes into metallic gold (Au) nano-particles, thereby mediating the (trans)formation of Au nuggets in Earth surface environments. In this study we describe a novel detoxification pathway, which prevents synergistic copper (Cu)/Au-toxicity. Gold-complexes and Cu-ions exert cooperative toxicity, because cellular uptake of Au(i/iii)-complexes blocks Cu(i) export from the cytoplasm by the Cu-efflux pump CupA. Using a combination of micro-analytical and biochemical methods we show that inducible resistance to these Cu/Au mixtures is mediated by the periplasmic Cu(i)-oxidase CopA, which functions as an oxygen-consuming Au(i)-oxidase. With high Au-complex loads the enzymatic activity of CopA detoxifies the reduction pathway of Au(iii)-complexes via Au(i)-intermediates to Au(0) nanoparticles in the periplasm. Thereby the concentration of highly toxic Au(i) in the cytoplasm is diminished, while allowing direct reduction of Au(iii) to Au nanoparticles in the periplasm. This permits C. metallidurans to thrive in Au-rich environments and biomineralise metallic Au.
金属光泽杆菌能够将有毒的金（Au）-配合物还原为金属金纳米颗粒，从而介导地球表面环境中金块的（转化）。在这项研究中，我们描述了一种新的解毒途径，该途径可防止协同的铜（Cu）/Au 毒性。金配合物和 Cu 离子具有协同毒性，因为细胞摄取 Au(i/iii)-配合物会阻止 Cu 外排泵 CupA 将 Cu(i)从细胞质中排出。我们使用微分析和生化方法的组合表明，对这些 Cu/Au 混合物的诱导抗性是由周质 Cu(i)-氧化酶 CopA 介导的，CopA 作为一种耗氧的 Au(i)-氧化酶发挥作用。在高 Au 配合物负载下，CopA 的酶活性通过 Au(i)-中间体将 Au(iii)-配合物的还原途径解毒为周质中的 Au(0)纳米颗粒。由此，细胞质中高毒性的 Au(i)浓度降低，同时允许在周质中直接将 Au(iii)还原为 Au 纳米颗粒。这使得金属光泽杆菌能够在富含 Au 的环境中茁壮成长并生物矿化金属 Au。
