Biomimetic synthesis of calcium-strontium apatite hollow nanospheres

Gan, Yong X.; Han, Dongmei; Gu, Fubo; Wang, Zhihua; Guo, Guangsheng

doi:10.1007/s11426-010-3171-4

Cited by 7 publications

(2 citation statements)

References 37 publications

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“…In the calcification experiment with purified PHO A, we obtained ovoid structures, measuring ∼2 µm in diameter, which could easily be confused with calcified bacteria based on SEM only (Figures 6A-D). Similar objects, sometimes referred to as spherules or microspheres and composed of apatite or octocalcium phosphate, have been obtained in the past by abiotic synthesis (Van Kemenade and de Bruyn, 1987;Kniep and Simon, 2007;Sun et al, 2009;Teshima et al, 2009;Gan et al, 2010;Perez et al, 2011). Therefore, SEM images should be considered only very cautiously for inferring the biogenicity of objects in phosphorites.…”

Section: Interpretation Of Putative Microbial Fossils In Phosphoritesmentioning

confidence: 93%

Calcium-Phosphate Biomineralization Induced by Alkaline Phosphatase Activity in Escherichia coli: Localization, Kinetics, and Potential Signatures in the Fossil Record

et al. 2015

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International audienceBacteria are thought to play an important role in the formation of calcium-phosphate minerals composing marine phosphorites, as supported by the common occurrence of fossil microbes in these rocks. Phosphatase enzymes may play a key role in this process. Indeed, they may increase the supersaturation with respect to Ca-phosphates by releasing orthophosphate ions following hydrolysis of organic phosphorus. However, several questions remain unanswered about the cellular-level mechanisms involved in this model, and its potential signatures in the mineral products. We studied Ca-phosphate precipitation by different strains of Escherichia coli which were genetically modified to differ in the abundance and cellular localization of the alkaline phosphatase (PHO A) produced. The mineral precipitated by either E. coli or purified PHO A was invariably identified as a carbonate-free non-stoichiometric hydroxyapatite. However, the bacterial precipitates could be discriminated from the ones formed by purified PHO A at the nano-scale. PHO A localization was shown to influence the pattern of Ca-phosphate nucleation and growth. Finally, the rate of calcification was proved to be consistent with the PHO A enzyme kinetics. Overall, this study provides mechanistic keys to better understand phosphogenesis in the environment, and experimental references to better interpret the microbial fossil record in phosphorites

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Section: Interpretation Of Putative Microbial Fossils In Phosphoritesmentioning

confidence: 93%

Calcium-Phosphate Biomineralization Induced by Alkaline Phosphatase Activity in Escherichia coli: Localization, Kinetics, and Potential Signatures in the Fossil Record

et al. 2015

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“…Hollow apatite spheres have been produced for biomedical applications based on several abiotic chemical processes (e.g., (Li et al, 1993;Kim et al, 2007;Teshima et al, 2009;Gan et al, 2010;Perez et al, 2011). The produced spheres measure between a few tens and a few hundreds of micrometers, with a broad size distribution.…”

Section: Figmentioning

confidence: 99%

Nanometer‐scale characterization of exceptionally preserved bacterial fossils in Paleocene phosphorites from Ouled Abdoun (Morocco)

et al. 2013

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Micrometer-sized spherical and rod-shaped forms have been reported in many phosphorites and often interpreted as microbes fossilized by apatite, based on their morphologic resemblance with modern bacteria inferred by scanning electron microscopy (SEM) observations. This interpretation supports models involving bacteria in the formation of phosphorites. Here, we studied a phosphatic coprolite of Paleocene age originating from the Ouled Abdoun phosphate basin (Morocco) down to the nanometer-scale using focused ion beam milling, transmission electron microscopy (TEM), and scanning transmission x-ray microscopy (STXM) coupled with x-ray absorption near-edge structure spectroscopy (XANES). The coprolite, exclusively composed of francolite (a carbonate-fluroapatite), is formed by the accumulation of spherical objects, delimited by a thin envelope, and whose apparent diameters are between 0.5 and 3 μm. The envelope of the spheres is composed of a continuous crown dense to electrons, which measures 20-40 nm in thickness. It is surrounded by two thinner layers that are more porous and transparent to electrons and enriched in organic carbon. The observed spherical objects are very similar with bacteria encrusting in hydroxyapatite as observed in laboratory experiments. We suggest that they are Gram-negative bacteria fossilized by francolite, the precipitation of which started within the periplasm of the cells. We discuss the role of bacteria in the fossilization mechanism and propose that they could have played an active role in the formation of francolite. This study shows that ancient phosphorites can contain fossil biological subcellular structures as fine as a bacterial periplasm. Moreover, we demonstrate that while morphological information provided by SEM analyses is valuable, the use of additional nanoscale analyses is a powerful approach to help inferring the biogenicity of biomorphs found in phosphorites. A more systematic use of this approach could considerably improve our knowledge and understanding of the microfossils present in the geological record.

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Advances in synthesis of calcium phosphate crystals with controlled size and shape

2014

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Biomimetic synthesis of calcium-strontium apatite hollow nanospheres

Cited by 7 publications

References 37 publications

Calcium-Phosphate Biomineralization Induced by Alkaline Phosphatase Activity in Escherichia coli: Localization, Kinetics, and Potential Signatures in the Fossil Record

Calcium-Phosphate Biomineralization Induced by Alkaline Phosphatase Activity in Escherichia coli: Localization, Kinetics, and Potential Signatures in the Fossil Record

Nanometer‐scale characterization of exceptionally preserved bacterial fossils in Paleocene phosphorites from Ouled Abdoun (Morocco)

Advances in synthesis of calcium phosphate crystals with controlled size and shape

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