Franco Chinese Biomineralization and Nano Structures Laboratory

Beijing, China

Franco Chinese Biomineralization and Nano Structures Laboratory

Beijing, China

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Wu W.,CAS Institute of Geology and Geophysics | Wu W.,Franco Chinese Biomineralization and Nano Structures Laboratory | Li Y.,University of Hong Kong | Pan Y.,CAS Institute of Geology and Geophysics | Pan Y.,Franco Chinese Biomineralization and Nano Structures Laboratory
Scientia Geologica Sinica | Year: 2012

Late Achaean to Palaeoproterozoic deposition of banded iron formations (BIF) is the most important iron ore resource on Earth. As evident by stable isotopes compositions, fossil molecule, rock magnetic properties, microorganisms such as cyanobacteria, iron-oxidizing and iron-reducing bacteria are suggested to have participated in the deposition of BIF. In this review, we briefly introduced the global distribution of BIF and the environments of early Precambrian Earth; then we went through the recent studies on bacterial mineralization related to the deposition of banded iron, including oxygenic/anoxygenic photosynthesis and dissimilatory iron reduction. Finally, we proposed some challenges and prospective. We suggest three approaches to understand the microbial mediated deposition of BIF: Searching for organic and inorganic signatures of bacterial mineralization, investigating the microbial participation in modern iron deposition in aquatic environments comparable to the microbial process of BIF, and laboratory microbial mineralization simulation, aiming at promoting the research on BIF formation mechanism.


Wu W.-F.,CAS Institute of Geology and Geophysics | Wu W.-F.,University of Chinese Academy of Sciences | Wu W.-F.,Franco Chinese Biomineralization and Nano structures Laboratory | Li J.-H.,CAS Institute of Geology and Geophysics | And 4 more authors.
Chinese Journal of Geophysics (Acta Geophysica Sinica) | Year: 2010

Single domain (SD) magnetite particles are significant magnetic carriers in geologic samples. However, its stability remains a major concern due to their fine-grain sizes. To probe the effects of organic matter on thermal stability of magnetite nanoparticles, we comparatively studied the thermo-magnetic properties, hysteresis parameters and low-temperature magnetic behaviors of isolated magnetosome magnetites of Magnetospirillum magiieticum AMB-1 and whole cell samples. The isolated SD magnetosome magentites with few amount of organic matter showed extremely good thermal stability, while the SD magnetites in whole cells changed strikingly during thermal treatment. The latter began to convert by ∼ 270°C, and were almost entirely reduced to paramagnetic substance by 400°C. The coercivity (Bc), remanent coercivity (B cr) and the ratio of saturation remanence to saturation magnetization (Mcr/Ms) decreased, while the ratio of remanence coercivity to coercivity (Bcr/Bc) increased when heating up to 400°C, owing to the reduction and decomposition of organic matter in whole cell. Our results indicated that SD magnetite in geologic samples carrying substantial organic matter can be hardly preserved if the samples were once heated to 300°C∼400°C.


Li B.,CAS Institute of Geology and Geophysics | Li B.,University of Chinese Academy of Sciences | Li B.,Franco Chinese Biomineralization and Nano structures Laboratory | Wu W.-F.,CAS Institute of Geology and Geophysics | And 6 more authors.
Chinese Journal of Geophysics (Acta Geophysica Sinica) | Year: 2011

The superparamagnetic (SP) magnetite produced by microorganism is an important source of magnetic minerals in sediments and soils. To investigate the behavior of the biomineralization, we compared the reduction of hydrous iron oxide and the formation of magnetite by iron reducing bacteria Shewanella putrefaciens CN32 at different temperatures (20°C, 30°C,37°C). It was observed that after the addition of bacteria to the system, the Eh began to decrease quickly while the pH and the concentration of ferrous increased, and the formation of magnetite started. Transmission electron microscopy observation and magnetic hysteresis loop of room temperature show that superparamagnetic magnetite was produced. Comparing the variations of susceptibility and isothermal remanent magnetization in different conditions suggests that temperature is the most important factor influencing the biomineralization, the increase of the temperature accelerated the mineralization. The fact that coercivity increased with the temperature and low temperature magnetic measurement suggests that the average blocking temperature (Tb) of the magnetite increased from 95K at 20°C to 160K at 37°C , both indicating that the size of the particles increased. Also the addition of AQDS (2, 6-anthraquinone disulphonate) as the electron shuttle accelerated the biomineralization by CN32. These results help us to understand the biomineralization capability of iron reducing bacteria and their contribution to the environmental magnetism.

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