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Abiotic hydroxylamine nitrification involving manganese- and iron-bearing minerals.

ABSTRACT: Hydroxylamine (NH2OH) undergoes biotic and abiotic transformation processes in soil, producing nitrous oxide gas (N2O(g)). Little is known about the magnitude of the abiotic chemical processes in the global N cycle, and the role of abiotic nitrification is still neglected in most current nitrogen trace gas studies. The abiotic fate of NH2OH in soil systems is often focused on transition metals including manganese (Mn) and iron (Fe), and empirical correlations of nitrogen residual species including nitrite (NO2-), nitrate (NO3-), and N2O(g). In this study, abiotic NH2OH nitrification by well-characterized manganese (Mn)- and iron (Fe)-bearing minerals (pyrolusite, amorphous MnO2(s), goethite, amorphous FeOOH(s)) was investigated. A nitrogen mass balance analysis involving NH2OH, and the abiotic nitrification residuals, N2O(g), N2O(aq), NO2-, NO3-, was used, and specific reactions and mechanisms were investigated. Rapid and complete NH2OH nitrification occurred (4-5?h) in the presence of pyrolusite and amorphous MnO2(s), achieving a 95-96% mass balance of N byproducts. Conversely, NH2OH nitrification was considerably slower by amorphous FeOOH(s) (14.5%) and goethite (1.1%). Direct reactions between the Mn- and Fe-bearing mineral species and NO2- and NO3- were not detected. Brunauer-Emmett-Teller surface area and energy dispersive X-ray measurements for elemental composition were used to determine the specific concentrations of Mn and Fe. Despite similar specific concentrations of Mn and Fe in crystalline and amorphous minerals, the rate of NH2OH nitrification was much greater in the Mn-bearing minerals. Results underscore the intrinsically faster NH2OH nitrification by Mn minerals than Fe minerals.

SUBMITTER: Rue K

PROVIDER: S-EPMC7286054 | biostudies-literature | 2018 Dec

REPOSITORIES: biostudies-literature

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Abiotic hydroxylamine nitrification involving manganese- and iron-bearing minerals.

Rue Kristie K Rusevova Klara K Biles Caleb L CL Huling Scott G SG

The Science of the total environment 20180711

Hydroxylamine (NH2OH) undergoes biotic and abiotic transformation processes in soil, producing nitrous oxide gas (N2O(g)). Little is known about the magnitude of the abiotic chemical processes in the global N cycle, and the role of abiotic nitrification is still neglected in most current nitrogen trace gas studies. The abiotic fate of NH2OH in soil systems is often focused on transition metals including manganese (Mn) and iron (Fe), and empirical correlations of ...[more]

PMID: 29990906

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Project description:Magnetotactic bacteria (MTB) are prokaryotes that form intracellular magnetite (Fe3O4) or greigite (Fe3S4) nanocrystals with tailored sizes, often in chain configurations. Such magnetic particles are each surrounded by a lipid bilayer membrane, called a magnetosome, and provide a model system for studying the formation and function of specialized internal structures in prokaryotes. Using fluorescence-coupled scanning electron microscopy, we identified a novel magnetotactic spirillum, XQGS-1, from freshwater Xingqinggong Lake, Xi'an City, Shaanxi Province, China. Phylogenetic analyses based on 16S rRNA gene sequences indicate that strain XQGS-1 represents a novel genus of the Alphaproteobacteria class in the Proteobacteria phylum. Transmission electron microscopy analyses reveal that strain XQGS-1 forms on average 17 ± 3 magnetite magnetosome particles with an ideal truncated octahedral morphology, with an average length and width of 88.3 ± 11.7 nm and 83.3 ± 11.0 nm, respectively. They are tightly organized into a single chain along the cell long axis close to the concave side of the cell. Intrachain magnetic interactions likely result in these large equidimensional magnetite crystals behaving as magnetically stable single-domain particles that enable bacterial magnetotaxis. Combined structural and chemical analyses demonstrate that XQGS-1 cells also biomineralize intracellular amorphous calcium phosphate (2 to 3 granules per cell; 90.5- ± 19.3-nm average size) and weakly crystalline calcium carbonate (2 to 3 granules per cell; 100.4- ± 21.4-nm average size) in addition to magnetite. Our results expand the taxonomic diversity of MTB and provide evidence for intracellular calcium phosphate biomineralization in MTB. IMPORTANCE Biomineralization is a widespread process in eukaryotes that form shells, teeth, or bones. It also occurs commonly in prokaryotes, resulting in more than 60 known minerals formed by different bacteria under wide-ranging conditions. Among them, magnetotactic bacteria (MTB) are remarkable because they might represent the earliest organisms that biomineralize intracellular magnetic iron minerals (i.e., magnetite [Fe3O4] or greigite [Fe3S4]). Here, we report a novel magnetotactic spirillum (XQGS-1) that is phylogenetically affiliated with the Alphaproteobacteria class. In addition to magnetite crystals, XQGS-1 cells form intracellular submicrometer calcium carbonate and calcium phosphate granules. This finding supports the view that MTB are also an important microbial group for intracellular calcium carbonate and calcium phosphate biomineralization.

Dataset Information

Abiotic hydroxylamine nitrification involving manganese- and iron-bearing minerals.

Publications

Abiotic hydroxylamine nitrification involving manganese- and iron-bearing minerals.

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