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Morphological, Microstructural, and In Situ Chemical Characteristics of Siderite Produced by Iron-Reducing Bacteria
Xiaohua Han1,2,3,4, Fuxian Wang1,2,3,4, Shiling Zheng5
1Key Laboratory of Earth and Planetary Physics, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China.
Environmental Science & Technology
|May 14, 2024
Summary
Dissimilatory iron-reducing bacteria (DIRB) create siderite minerals through a multistep growth process. These biogenic siderite particles exhibit unique shapes and contain organic molecules, offering insights into microbial iron cycling.
Area of Science:
- Geochemistry
- Microbiology
- Biomineralization
Background:
- Dissimilatory iron-reducing bacteria (DIRB) produce Fe(II)-bearing minerals like magnetite and siderite.
- The mineralization process and mechanisms of siderite formation by DIRB are not well understood compared to magnetite.
Purpose of the Study:
- To investigate the morphological, structural, and chemical features of biogenic siderite.
- To elucidate the mineralization process and assembly mechanisms of siderite produced by *Shewanella oneidensis* MR-4.
Main Methods:
- Growth experiment using *Shewanella oneidensis* MR-4.
- Advanced electron microscopy.
- Synchrotron-based scanning transmission X-ray microscopy (STXM).
Main Results:
- Fe(II) ions reacted with CO3^2- to form micrometer-sized siderite with diverse shapes (spindle, rod, peanut, dumbbell, sphere).
- Biogenic siderite particles consist of fanned-out single-crystal plates originating from a central core.
- STXM revealed the presence of ferrihydrite (Fh) and organic molecules within the siderite structure.
Conclusions:
- DIRB induce siderite biomineralization and assembly through a successive multistep growth process.
- Distinctive particle shapes and internal organic molecules are characteristic features of biogenic siderite.
- The findings provide evidence for siderite crystal assembly around a ferrihydrite-organic molecule core.
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