Stabilization of extracellular polymeric substances (Bacillus subtilis) by adsorption to and coprecipitation with Al forms

Abstract

Stabilization of extracellular polymeric substances (Bacillus subtilis) by adsorption to and coprecipitation with Al forms Mikutta, R.; Zang, U.; Chorover, J.; Haumaier, L.; Kalbitz, K. General rightsIt is not permitted to download or to forward/distribute the text or part of it without the consent of the author(s) and/or copyright holder(s), other than for strictly personal, individual use, unless the work is under an open content license (like Creative Commons). Disclaimer/Complaints regulationsIf you believe that digital publication of certain material infringes any of your rights or (privacy) interests, please let the Library know, stating your reasons. In case of a legitimate complaint, the Library will make the material inaccessible and/or remove it from the website. Please Ask the Library: http://uba.uva.nl/en/contact, or a letter to: Library of the University of Amsterdam, Secretariat, Singel 425, 1012 WP Amsterdam, The Netherlands. You will be contacted as soon as possible. Abstract Extracellular polymeric substances (EPS) are continuously produced by bacteria during their growth and metabolism. In soils, EPS are bound to cell surfaces, associated with biofilms, or released into solution where they can react with other solutes and soil particle surfaces. If such reaction results in a decrease in EPS bioaccessibility, it may contribute to stabilization of microbial-derived organic carbon (OC) in soil. Here we examined: (i) the chemical fractionation of EPS produced by a common Gram positive soil bacterial strain (Bacillus subtilis) during reaction with dissolved and colloidal Al species and (ii) the resulting stabilization against desorption and microbial decay by the respective coprecipitation (with dissolved Al) and adsorption (with Al(OH) 3(am) ) processes. Coprecipitates and adsorption complexes obtained following EPS-Al reaction as a function of pH and ionic strength were characterized by Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS). The stability of adsorbed and coprecipitated EPS against biodegradation was assessed by mineralization experiments for 1100 h. Up to 60% of the initial 100 mg/L EPS-C was adsorbed at the highest initial molar Al:C ratio (1.86), but this still resulted only in a moderate OC mass fraction in the solid phase (17 mg/g Al(OH) 3(am) ). In contrast, while coprecipitation by Al was less efficient in removing EPS from solution (maximum values of 33% at molar Al:C ratios of 0.1-0.2), the OC mass fraction in the solid product was substantially larger than that in adsorption complexes. Organic P compounds were preferentially bound during both adsorption and coprecipitation. Data are consistent with strong ligand exchange of EPS phosphoryl groups during adsorption to Al(OH) 3(am) , whereas for coprecipitation weaker sorption mechanisms are also involved. X-ray photoelectron analyses indicate an intimate mixing of EPS with Al in the coprecipitates, which is not observed in the case of EPS adsorption complexes. The incubation experiments...

Aggregate Stability in Soil with Humic and Histic Horizons in a Toposequence under Araucaria Forest

“…The SOM effect on aggregation has traditionally been attributed to the inner sphere complexes between the carboxyl groups and cations of the mineral structure by the ligand exchange mechanism (Chorover and Amistadi, 2001;Mikutta et al, 2011). Others types of organo-mineral interactions are also proposed: i) hydrophobic interactions; ii) C-O-alkyl groups and mineral hydroxyls; iii) cation bridges; iv) anion and cation exchange; and v) Van der Waals interactions (Stumm, 1992;Dick et al, 2009;Hanke et al, 2015).…”

“…Recent theoretical models hold that hydrophilic groups, which are abundant in oxidizing environments, interact directly with the mineral surface; this occurs mainly with Fe and Al oxides, due to their high density of monocoordinated hydroxyls (Krull et al, 2003;Schöning et al, 2005;Wiseman and Püttmann, 2006;Mikutta et al, 2011). Some studies have indicated that in aerobic soils, the surface of Fe oxides can interact directly with carbohydrate-like structures that are more labile compounds, and not only via ligand exchange with carboxyl groups (Miltner and Zech, 1998;Schöning et al, 2005).…”

Effects of litter traits, soil biota, and soil chemistry on soil carbon stocks at a common garden with 14 tree species

“…For example, protons and organic acids released by plants, or produced during oxidation of plant litter, can lower soil pH, promote mineral dissolution, and increase the concentration of Al and iron (Fe) in soil solution (Binkley and Richter 1987;van Breemen et al 1983). Monomeric and colloidal Al and Fe can then react with biomolecules to form complexes that deter microbial degradation, facilitating retention of soil organic C and N Mikutta et al 2011;Scheel et al 2008). Degradation of soil organic substrates can also be inhibited at low soil pH due to toxicity of Al ions (Scheel et al 2008), reduced exoenzyme activity (Sinsabaugh et al 2008), or shifts in microbial community composition (Fierer et al 2009).…”

Influência da Matéria Orgânica no Diâmetro Médio de Minerais da Fração Argila de Solos Desenvolvidos de Basalto no Sul do Brasil

“…O pH do ponto de carga zero (pH PCZ) desses óxidos é elevado, com valores entre sete e nove; no pH normal de solos tropicais e subtropicais (4-7) há predomínio desses grupos em suas formas protonadas (-AlOH 2 +0,5 e -FeOH 2 +0,5 ) (Schwertmann e Taylor, 1989), que facilitam a adsorção de compostos orgânicos. A grande densidade de hidroxilas monocoordenadas na superfície dos óxidos de Fe, como hematita (Hm) e goethita (Gt), pode levar à formação de interações fortes, como complexos de esfera interna, entre os grupos orgânicos e os minerais (Schwertmann e Taylor, 1989;Omoike e Chorover, 2006;Mikutta et al, 2011).…”

“…Mudanças no estádio de oxidação do metal, ocasionadas pela transferência de elétrons pelo ligante durante a formação do complexo, também podem influenciar o processo de dissolução, por meio da alteração do raio iônico do metal. Durante a formação do cristal, a formação de complexos pode ainda inibir ou retardar o crescimento de determinado plano cristalográfico (Omoike e Chorover, 2006;Mikutta et al, 2011;Henneberry et al, 2012).…”