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Magnetite nanoparticles modulate microbial nitrate reduction pathway
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DOI：10.1016/j.epsl.2024.119198.png)
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Abstract
En 中文
Magnetite nanoparticles (NPs) are among the most abundant iron-bearing minerals in various environments, and exhibit nanoscale effects, mixed valence states, and semiconducting properties. These characteristics enable them to play a critical role in the (bio-)geochemical cycling of essential elements for life. Emerging research has suggested that magnetite NPs may participate in microbial nitrate reduction, an important biogeochemical process occurring within redox-stratified ferruginous oceans during the Paleoproterozoic era (2.5-1.6 Ga) and in other marine systems. However, the precise effects and underlying mechanisms of magnetite NPs in this context remain largely unclear. To address these knowledge gaps, a series of anaerobic bench-scale experiments were conducted in this study using the Fe(II)-dependent denitrifying bacterium Pseudogulbenkiania sp. strain 2002 and magnetite NPs at various acetate concentrations. Our results show that, in the absence of magnetite, nitrogenous gases (N2O/N2) are the major products of microbial nitrate reduction by strain 2002, with only trace amounts of ammonium (NH4+) being detected. Interestingly, the presence of magnetite NPs significantly enhances NH4+ yields, especially in systems featuring smaller magnetite crystal sizes and lower acetate concentrations. Subsequent chemical, magnetic, and mineralogical analyses reveal that magnetite NPs undergo partial maghemitization during microbial nitrate reduction. These findings demonstrate that denitrifying microbes can partially switch from denitrification to dissimilatory nitrate reduction to ammonium (DNRA) in the presence of magnetite NPs. Such metabolic flexibility has significant implications for nitrogen retention in ferruginous water bodies, which were predominant in the Precambrian oceans.
Keywords:
Microbial denitrification
Magnetite nanoparticles
Nitrogen retention
DNRA
Paleoproterozoic nitrogen cycling
Journal
IF:
5.1
Papers:
804
Citations:
6.9W