Voici les éléments 1 - 10 sur 19
- PublicationMétadonnées seulementIdentification of active oxalotrophic bacteria by Bromodeoxyuridine DNA labeling in a microcosm soil experiments(2013)
; ;Martin, Gaëtan ;David, Maude M ; ;
- PublicationAccès libreBiologically induced mineralization in the tree Milicia excelsa (Moraceae) : its causes and consequences to the environment(2004)
;Braissant, Olivier ; ;Iroko trees (Milicia excelsa) in Ivory Coast and Cameroon are unusual because of their highly biomineralized tissues, which can virtually transform the trunk into stone. Oxalic acid (C2O4H2) and metal-oxalate play important roles in their ecosystems. In this study, the various forms of oxalate and carbonate mineralization reactions are investigated by using scanning electron microscopy and X-ray diffraction. Calcium oxalate monohydrate is associated with stem, bark and root tissues, whereas calcium oxalate dihydrate is found with wood rot fungi in soils, as well as in decaying wood. Laboratory cultures show that many soil bacteria are able to oxidize calcium oxalate rapidly, resulting in an increase in solution pH. In terms of M. excelsa, these transformations lead to the precipitation of calcium carbonate, not only within the wood tissue, but also within the litter and soil. We calculate that c. 500 kg of inorganic carbon is accumulated inside an 80-year-old tree, and c. 1000 kg is associated with its surrounding soil. Crucially, the fixation of atmospheric CO2 during tree photosynthesis, and its ultimate transformation into calcite, potentially represents a long-term carbon sink, because inorganic carbon has a longer residence time than organic carbon. Considering that calcium oxalate biosynthesis is widespread in the plant and fungal kingdoms, the biomineralization displayed by M. excelsa may be an extremely common phenomena.
- PublicationMétadonnées seulementTranslation of energy into morphology: Simulation of stromatolite morphospace using a stochastic model(: Elsevier Science Bv, 2004)
;Dupraz, Christophe ;Pattisina, RonnyStromatolites are examples of ail iterative system involving radiate accretive growth of microbial mats, biofilm and/or minerals that result from interaction between intrinsic and extrinsic factors, which progressively shape the final morphology. These interactions call neither be easily described by simple mathematical equations, nor by simple physical laws or chemical reactions. Therefore, a holistic approach that will reduce the system to a set of variables (which are combinations of natural variables) is proposed in order to create virtual morphologies which will be compared with their natural counterparts. The combination of both Diffusion Limited Aggregation (DLA) and cellular automata (CA) allows the exploration of the stromatolite morphological space and a representation of the intrinsic and extrinsic factors responsible for natural stromatolite morphogenesis. The holistic approach provides a translation in simple parameters of (I) the way that energy, nutrients and sedimentary particles reach the active surface of a future build-up, (2) flow these elements are distributed and used in order to create morphology, and (3) how simple environmental parameters, such as sedimentation, can disturb morphogenesis. In addition, most Precambrian stromatolite morphologies that are impossible to produce with numerical modeling such as the Kardar-Parisi-Zhan (KPZ) equation can be simulated with the DLA-CA model and this, with a minimum set of variables. (c) 2005 Elsevier B.V. All rights reserved.
- PublicationMétadonnées seulementIsolation and characterization of oxalotrophic bacteria from tropical soils(2015-4-15)
; ;Braissant, Olivier ; ;
- PublicationAccès libre
- PublicationMétadonnées seulement
- PublicationAccès libreBiomineralization in plants as a long-term carbon sink(2004)
; ;Olivier BraissantCarbon sequestration in the global carbon cycle is almost always attributed to organic carbon storage alone, while soil mineral carbon is generally neglected. However, due to the longer residence time of mineral carbon in soils (102–106 years), if stored in large quantities it represents a potentially more efficient sink. The aim of this study is to estimate the mineral carbon accumulation due to the tropical iroko tree (Milicia excelsa) in Ivory Coast. The iroko tree has the ability to accumulate mineral carbon as calcium carbonate (CaCO3) in ferralitic soils, where CaCO3 is not expected to precipitate. An estimate of this accumulation was made by titrating carbonate from two characteristic soil profiles in the iroko environment and by identifying calcium (Ca) sources. The system is considered as a net carbon sink because carbonate accumulation involves only atmospheric CO2 and Ca from Ca-carbonate-free sources. Around one ton of mineral carbon was found in and around an 80-year-old iroko stump, proving the existence of a mineral carbon sink related to the iroko ecosystem. Conservation of iroko trees and the many other biomineralizing plant species is crucial to the maintenance of this mineral carbon sink.
- PublicationMétadonnées seulementExperimental calcium-oxalate crystal production and dissolution by selected wood-rot fungi(2011)
;Guggiari, Matteo ;Bloque, Raphael ; ; ;
- PublicationMétadonnées seulementFungi, bacteria and soil pH: the oxalate?carbonate pathway as a model for metabolic interaction(2012)
;Martin, Gaëtan ;Guggiari, Matteo ; ; ; ; ; ;
- PublicationMétadonnées seulementBacterially induced mineralization of calcium carbonate in terrestrial environments: the role of exopolysaccharides and amino acids(2003)
;Braissant, Olivier ; ;Dupraz, Christophe