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Removal Of Multi-heavy Metals Using Biogenic Manganese Oxides Generated By A Deep-sea Sedimentary Bacterium – Brachybacterium Sp. Strain Mn32

Wenming Wang, Zongze Shao, Yanjun Liu, Gejiao Wang

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A deep-sea manganese-oxidizing bacterium, Brachybacterium sp. strain Mn32, showed high Mn(II) resistance (MIC 55 mM) and Mn(II)-oxidizing/removing abilities. Strain Mn32 removed Mn(II) by two pathways: (1) oxidizing soluble Mn(II) to insoluble biogenic Mn oxides – birnessite (δ-MnO2 group) and manganite (γ-MnOOH); (2) the biogenic Mn oxides further adsorb more Mn(II) from the culture. The generated biogenic Mn oxides surround the cell surfaces of strain Mn32 and provide a high capacity to adsorb Zn(II) and Ni(II). Mn(II) oxidation by strain Mn32 was inhibited by both sodium azide and o-phenanthroline, suggesting the involvement of a metalloenzyme which was induced by Mn(II). X-ray diffraction analysis showed that the crystal structures of the biogenic Mn oxides were different from those of commercial pyrolusite (β-MnO2 group) and fresh chemically synthesized vernadite (δ-MnO2 group). The biogenic Mn oxides generated by strain Mn32 showed two to three times higher Zn(II) and Ni(II) adsorption abilities than commercial and fresh synthetic MnO2. The crystal structure and the biogenic MnO2 types may be important factors for the high heavy metal adsorption ability of strain Mn32. This study provides potential applications of a new marine Mn(II)-oxidizing bacterium in heavy metal bioremediation and increases our basic knowledge of microbial manganese oxidation mechanisms.