In this study, a series of reduction experiments were conducted using a representative uranyl per... more In this study, a series of reduction experiments were conducted using a representative uranyl peroxide nanocluster, U60 (K
... Fe-oxides and Fe-silicates are often found in close spatial association with bacteria, both i... more ... Fe-oxides and Fe-silicates are often found in close spatial association with bacteria, both in natural systems ([Konhauser et al., 1993] and [Fortin et al., 1998]) as well as in laboratory settings ([Fortin and Ferris, 1998] and [Urrutia and Beveridge, 1994]). ...
... All rights reserved. Cited By in Scopus (115). Permissions & Reprints. Cd adsorpt... more ... All rights reserved. Cited By in Scopus (115). Permissions & Reprints. Cd adsorption onto bacterial surfaces: A universal adsorption edge? Nathan Yee Corresponding Author Contact Information , E-mail The Corresponding Author , 1 and Jeremy Fein 1. ...
Organophosphate pesticides are currently the most commonly used pesticides, but the mechanisms of... more Organophosphate pesticides are currently the most commonly used pesticides, but the mechanisms of biodegradation of these compounds are often unknown. In this study, we constructed a ternary biodegradation system containing methyl parathion (MP), a bacterial strain of Pseudomonas sp. Z1 with capability of degrading MP and montmorillonite, which is a common clay mineral in soils. The role of interfacial reactions between montmorillonite and the MP degrader on the biodegradation of MP was investigated by batch adsorption as well as through semi-permeable membrane experiments. The contact between degrader and montmorillonite in biodegradation was also dynamically examined using in situ attenuated total reflectance Fourier transform infrared spectroscopy. The metabolic activity of the degrading bacteria was also assessed using an isothermal microcalorimetric technique. The results indicate that sorption of bacterial cells onto montmorillonite enhances the metabolic activity of the bacteria and hence the biodegradation of MP by the bacteria, and that an amide group on a bacterial surface protein is responsible for the bacterial adhesion onto the montmorillonite. This stimulated effect ceased when the bacteria were physically separated from the surface of the clay by a membrane, demonstrating the importance of sorption of both the bacteria and the MP in the biodegradation process.
Microbial activities play a central role in the global cycling of selenium. Microorganisms can re... more Microbial activities play a central role in the global cycling of selenium. Microorganisms can reduce, methylate, and assimilate Se, controlling the transport and fate of Se in the environment. However, the mechanisms controlling these microbial activities are still poorly understood. In particular, it is unknown how the negatively charged Se(IV) and Se(VI) oxyanions that dominate the aqueous Se speciation in oxidizing environments bind to negatively charged microbial cell surfaces in order to become bioavailable. Here, we show that the adsorption of selenite onto Bacillus subtilis bacterial cells is controlled by cell envelope sulfhydryl sites. Once adsorbed onto the bacteria, selenite is reduced and forms reduced organo-Se compounds (e.g., RS-Se-SR). Because sulfhydryl sites are present within cell envelopes of a wide range of bacterial species, sulfhydryl-controlled adsorption of selenite likely represents a general mechanism adopted by bacteria to make selenite bioavailable. The...
The anaerobic bacterium Geobacter bemidijensis Bem has the unique ability to both produce and deg... more The anaerobic bacterium Geobacter bemidijensis Bem has the unique ability to both produce and degrade methylmercury (MeHg). While the adsorption of MeHg onto bacterial surfaces can affect the release of MeHg into aquatic environments as well as the uptake of MeHg for demethylation, the binding of MeHg to the bacterial envelope remains poorly understood. In this study, we quantified the adsorption of MeHg onto G. bemidijensis and applied X-ray absorption spectroscopy (XAS) to elucidate the mechanism of MeHg binding. The results showed MeHg adsorption onto G. bemidijensis cell surfaces was rapid and occurred via complexation to sulfhydryl functional groups. Titration experiments yielded cell surface sulfhydryl concentrations of 3.8 ± 0.2 μmol/g (wet cells). A one-site adsorption model with MeHg binding onto sulfhydryl sites provided excellent fits to adsorption isotherms conducted at different cell densities. The log K binding constant of MeHg onto the sulfhydryl sites was determined ...
Journal of colloid and interface science, Jan 15, 2019
Over the past 40 years, laboratory experiments involving single metal-single sorbent systems have... more Over the past 40 years, laboratory experiments involving single metal-single sorbent systems have been conducted in order to determine thermodynamic stability constants for metal-bacteria and metal-mineral surface complexes. The component additivity (CA) approach to surface complexation modeling (SCM) represents one method for using these experimentally-derived stability constants to predict the extent of metal adsorption in complex, multi-sorbent systems. However, quantitative tests of the CA approach are rare due to difficulties in determining the distribution of metals in complex multi-sorbent systems. In this study, we use a novel technique that couples the use of a cadmium(Cd)-specific fluorescent probe with confocal scanning laser microscopy to quantify Cd adsorption to bacteria in fully hydrated multi-sorbent samples that contain different ratios of Bacillus subtilis bacterial cells, the clay mineral kaolinite, and the aqueous chelating ligand EDTA. In this approach, we direc...
In this study, the sorption of Hg(II), Cd(II), and Au(III) onto Bacillus subtilis biomass with an... more In this study, the sorption of Hg(II), Cd(II), and Au(III) onto Bacillus subtilis biomass with an elevated concentration of sulfhydryl sites, induced by adding excess glucose to the growth medium (termed 'High Sulfhydryl Bacillus subtilis' or HSBS) was compared to that onto B. subtilis biomass with a low concentration of sulfhydryl sites (termed 'Low Sulfhydryl Bacillus subtilis' or LSBS) and to sorption onto a commercially available cation exchange resin. Our results show that HSBS exhibits sorption capacities for the three studied metals that are two to five times greater than the sorption capacities of LSBS for these metals. After blocking the bacterial cell envelope sulfhydryl sites using a qBBr treatment, the sorption of the metals onto HSBS was significantly inhibited, indicating that the enhanced sorption onto HSBS was mainly due to the elevated concentration of sulfhydryl sites on the bacteria. A direct comparison of the removal capacity of the HSBS and that ...
Colloids and Surfaces A: Physicochemical and Engineering Aspects
ABSTRACT In this study, the adsorption behaviors of a range of metals onto multi-layered graphene... more ABSTRACT In this study, the adsorption behaviors of a range of metals onto multi-layered graphene oxide (GO) as a function of pH and metal:GO ratio were measured. The GO exhibited an affinity for the metals in the following order: Pb(II)>Cu(II)>>Cd(II)≈Ni(II)≈Zn(II)>Sr(II)≈Ca(II). A four discrete-site non-electrostatic surface complexation model was used to account for the observed adsorption behaviors. For most of the metals studied, we modeled the adsorption by invoking divalent cation binding onto two or more of the deprotonated GO surface sites. The stability constant for each metal-site complex was calculated from the modeling, and the resulting models in general yield good fits to the experimental data. The calculated stability constants exhibit a correlation to stability constants for the corresponding aqueous metal-acetate, or the corresponding metal-hydroxide complexes. The calculated stability constants and the derived relationships from this study enable preliminary but useful predictions of the extent of metal adsorption onto GO for metals which have yet to be studied experimentally, and we tested the accuracy of these predictions by estimating and measuring the extent of Nd(III) adsorption onto GO as a function of EDTA concentration. The predicted extent of Nd adsorption onto GO is within 5% of the measured extent of Nd adsorption in an EDTA-free solution, and the predicted Nd adsorption behavior with increasing EDTA concentration is also in reasonable agreement with the measurements. Our results demonstrate the high affinity that GO has for binding a wide range of aqueous metals, and the results can be used to estimate with a reasonable degree of certainty the distribution of metals in complex GO-bearing environmental or engineered systems.
Bacterial sulfhydryl sites can form strong complexes with chalcophilic metals such as Hg and Cd, ... more Bacterial sulfhydryl sites can form strong complexes with chalcophilic metals such as Hg and Cd, thereby affecting the fate, transport, and bioavailability of these metals in both natural and engineered systems. In this study, five bacterial species were cultured in M9 minimal media containing a range of glucose concentrations as carbon source and in a high-nutrient TSB medium enriched with 50 g/L of glucose, and the sulfhydryl site concentrations of the obtained biomass samples were determined through selective sulfhydryl site-blocking, potentiometric titrations, and surface complexation modeling. The experimental results show that the glucose concentration in the M9 minimal media strongly affects the concentration of sulfhydryl sites that are present on the bacteria, with higher glucose concentrations yielding higher bacterial sulfhydryl site concentrations for each species studied. In contrast, although adding 50 g/L of glucose to the TSB medium significantly increases the sulfhy...
In this study, we use the measured extent of metal adsorption onto bacterial cells to constrain a... more In this study, we use the measured extent of metal adsorption onto bacterial cells to constrain a linear free energy relationship that allows estimation of unknown stability constants for metal-bacterial surface complexes based on the value of corresponding aqueous metal-acetate stability constants. A previous study (Fein et al., 2001) used metal adsorption experiments to constrain a similar relationship, but the
... Christopher J. Daughney* † ‡ and Jeremy B. Fein §. Earth and Planetary ... coli Cell Surface.... more ... Christopher J. Daughney* † ‡ and Jeremy B. Fein §. Earth and Planetary ... coli Cell Surface. David Borrok, M. Jack Borrok, Jeremy B. Fein, and Laura L. Kiessling. Environmental Science & Technology 2005 39 (14), 5227-5233. ...
In this study, a series of reduction experiments were conducted using a representative uranyl per... more In this study, a series of reduction experiments were conducted using a representative uranyl peroxide nanocluster, U60 (K
... Fe-oxides and Fe-silicates are often found in close spatial association with bacteria, both i... more ... Fe-oxides and Fe-silicates are often found in close spatial association with bacteria, both in natural systems ([Konhauser et al., 1993] and [Fortin et al., 1998]) as well as in laboratory settings ([Fortin and Ferris, 1998] and [Urrutia and Beveridge, 1994]). ...
... All rights reserved. Cited By in Scopus (115). Permissions & Reprints. Cd adsorpt... more ... All rights reserved. Cited By in Scopus (115). Permissions & Reprints. Cd adsorption onto bacterial surfaces: A universal adsorption edge? Nathan Yee Corresponding Author Contact Information , E-mail The Corresponding Author , 1 and Jeremy Fein 1. ...
Organophosphate pesticides are currently the most commonly used pesticides, but the mechanisms of... more Organophosphate pesticides are currently the most commonly used pesticides, but the mechanisms of biodegradation of these compounds are often unknown. In this study, we constructed a ternary biodegradation system containing methyl parathion (MP), a bacterial strain of Pseudomonas sp. Z1 with capability of degrading MP and montmorillonite, which is a common clay mineral in soils. The role of interfacial reactions between montmorillonite and the MP degrader on the biodegradation of MP was investigated by batch adsorption as well as through semi-permeable membrane experiments. The contact between degrader and montmorillonite in biodegradation was also dynamically examined using in situ attenuated total reflectance Fourier transform infrared spectroscopy. The metabolic activity of the degrading bacteria was also assessed using an isothermal microcalorimetric technique. The results indicate that sorption of bacterial cells onto montmorillonite enhances the metabolic activity of the bacteria and hence the biodegradation of MP by the bacteria, and that an amide group on a bacterial surface protein is responsible for the bacterial adhesion onto the montmorillonite. This stimulated effect ceased when the bacteria were physically separated from the surface of the clay by a membrane, demonstrating the importance of sorption of both the bacteria and the MP in the biodegradation process.
Microbial activities play a central role in the global cycling of selenium. Microorganisms can re... more Microbial activities play a central role in the global cycling of selenium. Microorganisms can reduce, methylate, and assimilate Se, controlling the transport and fate of Se in the environment. However, the mechanisms controlling these microbial activities are still poorly understood. In particular, it is unknown how the negatively charged Se(IV) and Se(VI) oxyanions that dominate the aqueous Se speciation in oxidizing environments bind to negatively charged microbial cell surfaces in order to become bioavailable. Here, we show that the adsorption of selenite onto Bacillus subtilis bacterial cells is controlled by cell envelope sulfhydryl sites. Once adsorbed onto the bacteria, selenite is reduced and forms reduced organo-Se compounds (e.g., RS-Se-SR). Because sulfhydryl sites are present within cell envelopes of a wide range of bacterial species, sulfhydryl-controlled adsorption of selenite likely represents a general mechanism adopted by bacteria to make selenite bioavailable. The...
The anaerobic bacterium Geobacter bemidijensis Bem has the unique ability to both produce and deg... more The anaerobic bacterium Geobacter bemidijensis Bem has the unique ability to both produce and degrade methylmercury (MeHg). While the adsorption of MeHg onto bacterial surfaces can affect the release of MeHg into aquatic environments as well as the uptake of MeHg for demethylation, the binding of MeHg to the bacterial envelope remains poorly understood. In this study, we quantified the adsorption of MeHg onto G. bemidijensis and applied X-ray absorption spectroscopy (XAS) to elucidate the mechanism of MeHg binding. The results showed MeHg adsorption onto G. bemidijensis cell surfaces was rapid and occurred via complexation to sulfhydryl functional groups. Titration experiments yielded cell surface sulfhydryl concentrations of 3.8 ± 0.2 μmol/g (wet cells). A one-site adsorption model with MeHg binding onto sulfhydryl sites provided excellent fits to adsorption isotherms conducted at different cell densities. The log K binding constant of MeHg onto the sulfhydryl sites was determined ...
Journal of colloid and interface science, Jan 15, 2019
Over the past 40 years, laboratory experiments involving single metal-single sorbent systems have... more Over the past 40 years, laboratory experiments involving single metal-single sorbent systems have been conducted in order to determine thermodynamic stability constants for metal-bacteria and metal-mineral surface complexes. The component additivity (CA) approach to surface complexation modeling (SCM) represents one method for using these experimentally-derived stability constants to predict the extent of metal adsorption in complex, multi-sorbent systems. However, quantitative tests of the CA approach are rare due to difficulties in determining the distribution of metals in complex multi-sorbent systems. In this study, we use a novel technique that couples the use of a cadmium(Cd)-specific fluorescent probe with confocal scanning laser microscopy to quantify Cd adsorption to bacteria in fully hydrated multi-sorbent samples that contain different ratios of Bacillus subtilis bacterial cells, the clay mineral kaolinite, and the aqueous chelating ligand EDTA. In this approach, we direc...
In this study, the sorption of Hg(II), Cd(II), and Au(III) onto Bacillus subtilis biomass with an... more In this study, the sorption of Hg(II), Cd(II), and Au(III) onto Bacillus subtilis biomass with an elevated concentration of sulfhydryl sites, induced by adding excess glucose to the growth medium (termed 'High Sulfhydryl Bacillus subtilis' or HSBS) was compared to that onto B. subtilis biomass with a low concentration of sulfhydryl sites (termed 'Low Sulfhydryl Bacillus subtilis' or LSBS) and to sorption onto a commercially available cation exchange resin. Our results show that HSBS exhibits sorption capacities for the three studied metals that are two to five times greater than the sorption capacities of LSBS for these metals. After blocking the bacterial cell envelope sulfhydryl sites using a qBBr treatment, the sorption of the metals onto HSBS was significantly inhibited, indicating that the enhanced sorption onto HSBS was mainly due to the elevated concentration of sulfhydryl sites on the bacteria. A direct comparison of the removal capacity of the HSBS and that ...
Colloids and Surfaces A: Physicochemical and Engineering Aspects
ABSTRACT In this study, the adsorption behaviors of a range of metals onto multi-layered graphene... more ABSTRACT In this study, the adsorption behaviors of a range of metals onto multi-layered graphene oxide (GO) as a function of pH and metal:GO ratio were measured. The GO exhibited an affinity for the metals in the following order: Pb(II)>Cu(II)>>Cd(II)≈Ni(II)≈Zn(II)>Sr(II)≈Ca(II). A four discrete-site non-electrostatic surface complexation model was used to account for the observed adsorption behaviors. For most of the metals studied, we modeled the adsorption by invoking divalent cation binding onto two or more of the deprotonated GO surface sites. The stability constant for each metal-site complex was calculated from the modeling, and the resulting models in general yield good fits to the experimental data. The calculated stability constants exhibit a correlation to stability constants for the corresponding aqueous metal-acetate, or the corresponding metal-hydroxide complexes. The calculated stability constants and the derived relationships from this study enable preliminary but useful predictions of the extent of metal adsorption onto GO for metals which have yet to be studied experimentally, and we tested the accuracy of these predictions by estimating and measuring the extent of Nd(III) adsorption onto GO as a function of EDTA concentration. The predicted extent of Nd adsorption onto GO is within 5% of the measured extent of Nd adsorption in an EDTA-free solution, and the predicted Nd adsorption behavior with increasing EDTA concentration is also in reasonable agreement with the measurements. Our results demonstrate the high affinity that GO has for binding a wide range of aqueous metals, and the results can be used to estimate with a reasonable degree of certainty the distribution of metals in complex GO-bearing environmental or engineered systems.
Bacterial sulfhydryl sites can form strong complexes with chalcophilic metals such as Hg and Cd, ... more Bacterial sulfhydryl sites can form strong complexes with chalcophilic metals such as Hg and Cd, thereby affecting the fate, transport, and bioavailability of these metals in both natural and engineered systems. In this study, five bacterial species were cultured in M9 minimal media containing a range of glucose concentrations as carbon source and in a high-nutrient TSB medium enriched with 50 g/L of glucose, and the sulfhydryl site concentrations of the obtained biomass samples were determined through selective sulfhydryl site-blocking, potentiometric titrations, and surface complexation modeling. The experimental results show that the glucose concentration in the M9 minimal media strongly affects the concentration of sulfhydryl sites that are present on the bacteria, with higher glucose concentrations yielding higher bacterial sulfhydryl site concentrations for each species studied. In contrast, although adding 50 g/L of glucose to the TSB medium significantly increases the sulfhy...
In this study, we use the measured extent of metal adsorption onto bacterial cells to constrain a... more In this study, we use the measured extent of metal adsorption onto bacterial cells to constrain a linear free energy relationship that allows estimation of unknown stability constants for metal-bacterial surface complexes based on the value of corresponding aqueous metal-acetate stability constants. A previous study (Fein et al., 2001) used metal adsorption experiments to constrain a similar relationship, but the
... Christopher J. Daughney* † ‡ and Jeremy B. Fein §. Earth and Planetary ... coli Cell Surface.... more ... Christopher J. Daughney* † ‡ and Jeremy B. Fein §. Earth and Planetary ... coli Cell Surface. David Borrok, M. Jack Borrok, Jeremy B. Fein, and Laura L. Kiessling. Environmental Science & Technology 2005 39 (14), 5227-5233. ...
Uploads