Summary auto-generated
Researchers isolated Brachybacterium sp. strain Mn32, a deep-sea manganese-oxidizing bacterium from Pacific Ocean sediments, and investigated its ability to remove heavy metals. The bacterium removed Mn(II) through two mechanisms: oxidizing soluble Mn(II) into insoluble biogenic manganese oxides (birnessite and manganite) that accumulate on cell surfaces, and further adsorption of additional Mn(II) onto these oxide layers. Enzyme inhibitor experiments indicated that manganese oxidation involved a metalloenzyme activated by Mn(II) presence. The biogenic manganese oxides generated by strain Mn32 demonstrated remarkable capacity for removing zinc and nickel ions—absorbing 2-3 times more of these metals than commercial or synthetic manganese dioxide. X-ray diffraction analysis revealed the biogenic oxides had distinct crystal structures compared to abiogenic manganese dioxide forms, with birnessite being the predominant type produced. These structural differences likely account for the superior heavy metal adsorption properties. The findings suggest strain Mn32 has significant potential for bioremediation applications in treating multi-heavy-metal contaminated water.
Key findings
- Brachybacterium sp. strain Mn32 oxidizes Mn(II) into biogenic manganese oxides (birnessite and manganite) through enzyme-catalyzed mechanisms involving copper-dependent metalloenzymes
- The biogenic manganese oxides produced by strain Mn32 adsorb 2-3 times more zinc and nickel than commercial or synthetic manganese dioxide
- X-ray diffraction analysis showed biogenic manganese oxides have distinct, highly crystalline structures compared to poorly crystallized abiotic manganese oxides, with birnessite being the primary form
- Strain Mn32 demonstrated extremely high manganese resistance (MIC 55 mM) and accumulated manganese oxides on its cell surfaces
- The enzyme catalyzing Mn(II) oxidation is activated by Mn(II) presence and expressed during stationary phase growth
This summary was generated automatically from the article PDF and is not part of the original publication. Refer to the PDF for the authoritative text.
Abstract
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.