title: Bio-dissolution of colloidal-size clay minerals entrapped in microporous silica gels.
abstract: Four colloidal-size fractions of strongly anisotropic particles of nontronite (NAu-2) having different ratios of basal to edge surfaces were incubated in the presence of heterotrophic soil bacteria to evaluate how changes in mineral surface reactivity influence microbial dissolution rate of minerals. To avoid any particle aggregation, which could change the reactive surface area available for dissolution, NAu-2 particles were immobilized in a biocompatible TEOS-derived silica matrix. The resulting hybrid silica gels support bacterial growth with NAu-2 as the sole source of Fe and Mg. Upon incubation of the hybrid material with bacteria, between 0.3% and 7.5% of the total Fe included in the mineral lattice was released with a concomitant pH decrease. For a given pH value, the amount of released Fe varied between strains and was two to twelve-fold higher than under abiotic conditions. This indicates that complexing agents produced by bacteria play an important role in the dissolution process. However, in contrast with proton-promoted NAu-2 dissolution (abiotic incubations) that was negatively correlated with particle size, bacterial-enhanced dissolution was constant for all size fractions used. We conclude that bio-dissolution of nontronite particles under acidic conditions seems to be controlled by bacterial metabolism rather than by the surface reactivity of mineral.
authors.affiliation: LIMOS (Laboratoire des Interactions Microorganismes-Minéraux-Matière Organique dans les Sols), UMR 7137 CNRS, BP 70239, Vandoeuvre-lès-Nancy Cedex 54506, France. malgorzata.grybos@unilim.fr
authors.forename: Malgorzata
authors.initials: M
authors.lastname: Grybos
authors.forename: Patrick
authors.initials: P
authors.lastname: Billard
authors.forename: Sylvie
authors.initials: S
authors.lastname: Desobry-Banon
authors.forename: Laurent J
authors.initials: LJ
authors.lastname: Michot
authors.forename: Jean-François
authors.initials: JF
authors.lastname: Lenain
authors.forename: Christian
authors.initials: C
authors.lastname: Mustin
mesh_terms: D000538:Aluminum Silicates; D001419:Bacteria / Q000254:growth & development / Q000378:metabolism*; D000077215:Clay; D003102:Colloids; D006046:Gold; D006863:Hydrogen-Ion Concentration; D008903:Minerals / Q000378:metabolism*; D009584:Nitrogen; D016062:Porosity; D058428:Silica Gel; D012995:Solubility
chemical_list: D000538:Aluminum Silicates; D003102:Colloids; D008903:Minerals; D058428:Silica Gel; D006046:Gold; D009584:Nitrogen; D000077215:Clay