Search results for "mineralization"
showing 10 items of 312 documents
Characterization of an isoproturon mineralizing bacterial culture enriched from a French agricultural soil.
2009
The phenylurea herbicide isoproturon, 3-(4-isopropylphenyl)-1,1-dimethylurea (IPU), was found to be rapidly mineralized by a bacterial culture isolated from an agricultural soil regularly exposed to IPU. Molecular analysis of the bacterial culture by DNA fingerprinting, cloning and sequencing of the 16S rRNA genes revealed that it consisted of six different members among whom the dominant was related to Sphingomonas sp. Six bacterial strains belonging to genera Ancylobacter, Pseudomonas, Stenotrophomonas, Methylobacterium, Variovorax and Agrobacterium were isolated from the IPU-degrading culture. None of these were able to degrade IPU in pure culture and only the intact culture sustained th…
Self-healing, an intrinsic property of biomineralization processes
2013
The sponge siliceous spicules are formed enzymatically via silicatein, in contrast to other siliceous biominerals. Originally, silicatein had been described as a major structural protein of the spicules that has the property to allow a specific deposition of silica onto their surface. More recently, it had been unequivocally demonstrated that silicatein displays a genuine enzyme activity, initiating and maintaining silica biopolycondensation at low precursor concentrations (<2 mM). Even more, as silicatein becomes embedded into the biosilica polymer, formed by the enzyme, it retains its functionality to enable a controlled biosilica deposition. The protection of silicatein through the biosi…
Role of the fauna in soil processes: techniques using simulated forest floor
1991
Abstract Laboratory experiments were conducted to test the influence of soil animals on processes such as decomposition, nutrient cycling, and plant growth in northern coniferous forests. The techniques included simulation of a complex pattern of forest floor, controlled air flow through the systems, and automatic measurement of carbon flows. The soil fauna generally enhanced evolution of CO2 and mineralization of N and P from soil and litter, and increased considerably the biomass production and N content of birch seedlings. Significant results were also obtained on interactions between different faunal components.
Sedimentological and tectonic context of Paleoproterozoïque Franceville basin (Gabon) : fluid pressure structures, bitumen and uranium mineralization
2016
Metallogenic deposits within paleproterozoic basins depend on generation and migration of fluids. The aim of this study is to provide a better understanding of tectonic, sedimentological and diagenetic setting of the uranium deposits in the Franceville basin and to characterize hydraulic fracturing impact on fluid migration processes in sandstone reservoirs.Tectonic study define the N180-170° transfer faults, associated with Archean tectonic and the N110-120° longitudinal normal faults. These two fault directions split the Franceville basin into small sub-basins. The longitudinal normal faults are associated with footwall anticlines and hanging wall synclines. The uranium deposits of France…
The formation and mineralization of mollusk shell.
2011
27 pages; International audience; In the last years, the field of mollusk biomineralization has known a tremendous mutation. The most recent advances deal with the nanostructure of shell biominerals, and with the identification of several shell matrix proteins: on one hand, the complex hierarchical organization of shell biominerals has been deciphered in few models, like nacre. On the other hand, although proteins represent a minor shell component, they are the major macromolecules that control biocrystal synthesis. Until recently, the paradigm was to consider that this control occurs by two antagonist mechanisms: crystal nucleation and growth inhibition. Emerging models try to translate a …
The shell-forming proteome of Lottia gigantea reveals both deep conservations and lineage-specific novelties
2013
19 pages; International audience; Proteins that are occluded within the molluscan shell, the so-called shell matrix proteins (SMPs), are an assemblage of biomolecules attractive to study for several reasons. They increase the fracture resistance of the shell by several orders of magnitude, determine the polymorph of CaCO(3) deposited, and regulate crystal nucleation, growth initiation and termination. In addition, they are thought to control the shell microstructures. Understanding how these proteins have evolved is also likely to provide deep insight into events that supported the diversification and expansion of metazoan life during the Cambrian radiation 543 million years ago. Here, we p…
Direct dating of gold by radiogenic helium: Testing the method on gold from Diamantina, Minas Gerais, Brazil
2013
New analytical developments have made radiogenic helium ( 4 He) applicable to archeological gold artifacts for age determinations. Here we report the application of the U/Th– 4 He method to the direct dating of gold from the historically important gold deposit in Diamantina, Minas Gerais, Brazil. The U/Th– 4 He age of 515 ± 55 Ma for the Diamantina gold is corroborated by a new U/Pb age of 524 ± 16 Ma for rutile recovered from auriferous pockets. These ages tie the Diamantina gold mineralization to the Brasiliano orogenic event, in the context of the Gondwana amalgamation. Our results indicate that U/Th– 4 He dating of gold is possible, opening new perspectives for the dating of gold deposi…
Histochemical and electron microscopic analysis of spiculogenesis in the demosponge Suberites domuncula.
2006
The skeleton of demosponges is built of spicules consisting of biosilica. Using the primmorph system from Suberites domuncula, we demonstrate that silicatein, the biosilica-synthesizing enzyme, and silicase, the catabolic enzyme, are colocalized at the surface of growing spicules as well as in the axial filament located in the axial canal. It is assumed that these two enzymes are responsible for the deposition of biosilica. In search of additional potential structural molecules that might guide the mineralization process during spiculogenesis to species-specific spicules, electron microscopic studies with antibodies against galectin and silicatein were performed. These studies showed that …
Microradiography and confocal laser scanning microscopy applied to enamel lesions formed in vivo with and without fluoride varnish treatment
1996
The aim of the present investigation was to combine 2 techniques suitable for lesion characterization: quantitative microradiography (TMR) and confocal laser scanning microscopy (CLSM) on in vivo induced lesions with and without a fluoride varnish (Duraphat(R)) treatment. Orthodontic bands were attached to premolars to be extracted for orthodontic reasons to induce enamel caries on the buccal surfaces. In the caries development part of the study, 1 tooth of each pair received at the start 1 topical application with the fluoride varnish Duraphat(R), the contralateral tooth serving as untreated control. All teeth were extracted after 4 weeks. In the caries progression part, the premolars were…
Proteoglycan occurrence in gastrolith of the crayfish Cherax quadricarinatus (Malacostraca: Decapoda).
2012
14 pages; International audience; Biomineralized structures are hybrid composites formed and stabilized by the close interaction of the organic and the inorganic phases. Crayfish are good models for studying biomineralization because they develop, in a molting-mineralization cycle, semi-spherical mineralized structures referred to as gastroliths. The organic matrix of these structures consists of proteins, polysaccharides, and lipids. Chitin is the main polysaccharide and is concentrically arranged as fibrous chitin-protein lamellar structures. Although several proteins and low-molecular weight phosphorylated components have been reported to be involved in gastrolith mineralization, the occ…