Interactions of three soil bacteria species with phyllosilicate surfaces in hybrid silica gels

Abstract

To simulate iron consumption in soils, iron leaching from silicate minerals due to three heterotrophic bacterial strains and a chemical treatment was studied using hybrid silica gel (HSG) doped with two phyllosilicates, nontronite (NAu-2) or low-iron-content montmorillonite (SWy-2). HSG methodology, a novel way of separating bacteria cells from a colloidal mineral source, consisted in embedding colloidal mineral particles into an amorphous porous silica matrix using a classical sol-gel procedure. Pantoae agglomerans PA1 and Rahnella aquatilis RA1 were isolated from silicate-rich soils, that is, beech and wheat rhizospheres (Vosges, France); Burkholderia sp. G5 was selected from acidic and nutrient-poor podzol soils (Vosges, France). Fe release from clay minerals and production of bacterial metabolites, that is, low molecular weight organic acids (LMWOA) and siderophores, were monitored. Two LMWOA profiles were observed with major gluconate production (> 9000 μM) for Burkholderia sp. G5 and moderate production of lactate, acetate, propionate, formate, oxalate, citrate, and succinate (< 300 μM) for R. aquatilis RA1 and P. agglomerans PA1. HSG demonstrated its usefulness in revealing clay mineral-microorganisms interactions. The effect of bacterial exsudates was clearly separated from physical contact effect.

Siderophore-Mediated Iron Dissolution from Nontronites Is Controlled by Mineral Cristallochemistry

“…The average size of the particles used in the present study was 460 nm in length, 60 nm in width for NAu-1, 368 nm in length, 93 nm in width for NAu-2, and around 1 nm thickness for both nontronites (Michot et al, 2008 ). Hybrid silica gels were prepared by immobilization of nontronite particles in a microporous, tetraethylorthosilicate- (TEOS, Fluka) derived silica gels by a sol-gel technique as described previously (Grybos et al, 2010 , 2011 ; Oulkadi et al, 2014 ). For this study, the procedure was automated and silica gels were produced in 96-wells microplates (MTP 96/F-bottom, Eppendorf) with the use of epMotion 5070's automated pipetting system (Eppendorf).…”

Bioavailability of Colloidal Iron to Heterotrophic Bacteria in Sediments, and Effects on the Mobility of Colloid-Associated Metal(loid)s

“…In addition, the release of elements appears to be impacted by the type of bacteria even at similar pH conditions. Such a dependence on the type of bacteria may be explained by the diversity of the exudates produced, releasing organic ligands of different nature in different concentrations, as documented for soil microorganisms under similar experimental conditions [40]. It could also be due to the nature of the tested bacteria.…”

“…If HSG is allowed to separate bacteria from purified and size-calibrated clay minerals in order to deeply study the biochemical interactions at the colloidal particle-bacteria interface [23,39,40], we showed the feasibility of using such a methodology to study the ability of bacteria to sequester nutrients from sedimentary colloids that are heterogenous in size and chemical composition (Figure 1 and Table 2).…”