Vanadium Respiration by
            <i>Geobacter metallireducens</i>
            : Novel Strategy for In Situ Removal of Vanadium from Groundwater

Ortiz-Bernad, Irene; Anderson, Robert; Vrionis, Helen A.; Lovley, Derek R.

doi:10.1128/aem.70.5.3091-3095.2004

Cited by 213 publications

(128 citation statements)

References 27 publications

(31 reference statements)

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“…Geobacter species are important agents in the bioremediation of organic contaminants (Lovley et al, 1989;Rooney-Varga et al, 1999;Lin et al, 2005), as well as uranium (Anderson et al, 2003;North et al, 2004;Vrionis et al, 2005) and vanadium (Ortiz-Bernad et al, 2004b). Analysis of gene transcript abundance within the subsurface Geobacter community has been successful in diagnosing rates of metabolism in Geobacter species as well as nutrient limitations and stress responses (Holmes et al, 2004b(Holmes et al, , 2005O'Neil et al, 2008;Mouser et al, 2009a).…”

Section: Introductionmentioning

confidence: 99%

Molecular analysis of phosphate limitation in Geobacteraceae during the bioremediation of a uranium-contaminated aquifer

et al. 2009

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Nutrient limitation is an environmental stress that may reduce the effectiveness of bioremediation strategies, especially when the contaminants are organic compounds or when organic compounds are added to promote microbial activities such as metal reduction. Genes indicative of phosphatelimitation were identified by microarray analysis of chemostat cultures of Geobacter sulfureducens. This analysis revealed that genes in the pst-pho operon, which is associated with a high-affinity phosphate uptake system in other microorganisms, had significantly higher transcript abundance under phosphate-limiting conditions, with the genes pstB and phoU upregulated the most. Quantitative PCR analysis of pstB and phoU transcript levels in G. sulfurreducens grown in chemostats demonstrated that the expression of these genes increased when phosphate was removed from the culture medium. Transcripts of pstB and phoU within the subsurface Geobacter species predominating during an in situ uranium-bioremediation field experiment were more abundant than in chemostat cultures of G. sulfurreducens that were not limited for phosphate. Addition of phosphate to incubations of subsurface sediments did not stimulate dissimilatory metal reduction. The added phosphate was rapidly adsorbed onto the sediments. The results demonstrate that Geobacter species can effectively reduce U(VI) even when experiencing suboptimal phosphate concentrations and that increasing phosphate availability with phosphate additions is difficult to achieve because of the high reactivity of this compound. This transcript-based approach developed for diagnosing phosphate limitation should be applicable to assessing the potential need for additional phosphate in other bioremediation processes.

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Section: Introductionmentioning

confidence: 99%

Molecular analysis of phosphate limitation in Geobacteraceae during the bioremediation of a uranium-contaminated aquifer

et al. 2009

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“…They have been found to be ubiquitous in a myriad of subsurface environments. Detailed studies of their metabolism have revealed them to be capable of bioremediation of several heavy metals, including uranium, plutonium, technetium, and vanadium, as well as biodegradation of several organic contaminants, including monoaromatic hydrocarbons (16,17,26). More recently, Geobacter species have been used to generate electricity from waste organic matter (2, 15, 19).…”

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confidence: 99%

Flux Analysis of Central Metabolic Pathways in Geobacter metallireducens during Reduction of Soluble Fe(III)-Nitrilotriacetic Acid

Tang

Chakraborty

Martín

et al. 2007

Appl Environ Microbiol

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We analyzed the carbon fluxes in the central metabolism of Geobacter metallireducens strain GS-15 using 13 C isotopomer modeling. Acetate labeled in the first or second position was the sole carbon source, and Fenitrilotriacetic acid was the sole terminal electron acceptor. The measured labeled acetate uptake rate was 21 mmol/g (dry weight)/h in the exponential growth phase. The resulting isotope labeling pattern of amino acids allowed an accurate determination of the in vivo global metabolic reaction rates (fluxes) through the central metabolic pathways using a computational isotopomer model. The tracer experiments showed that G. metallireducens contained complete biosynthesis pathways for essential metabolism, and this strain might also have an unusual isoleucine biosynthesis route (using acetyl coenzyme A and pyruvate as the precursors). The model indicated that over 90% of the acetate was completely oxidized to CO 2 via a complete tricarboxylic acid cycle while reducing iron. Pyruvate carboxylase and phosphoenolpyruvate (PEP) carboxykinase were present under these conditions, but enzymes in the glyoxylate shunt and malic enzyme were absent. Gluconeogenesis and the pentose phosphate pathway were mainly employed for biosynthesis and accounted for less than 3% of total carbon consumption. The model also indicated surprisingly high reversibility in the reaction between oxoglutarate and succinate. This step operates close to the thermodynamic equilibrium, possibly because succinate is synthesized via a transferase reaction, and the conversion of oxoglutarate to succinate is a rate-limiting step for carbon metabolism. These findings enable a better understanding of the relationship between genome annotation and extant metabolic pathways in G. metallireducens.Geobacter species are known to be one of the dominant groups of microorganisms mediating iron reduction in the environment (21). They have been found to be ubiquitous in a myriad of subsurface environments. Detailed studies of their metabolism have revealed them to be capable of bioremediation of several heavy metals, including uranium, plutonium, technetium, and vanadium, as well as biodegradation of several organic contaminants, including monoaromatic hydrocarbons (16,17,26). More recently, Geobacter species have been used to generate electricity from waste organic matter (2, 15, 19). These unique metabolisms make Geobacter species important players in the contaminated subsurface environment (18). Geobacter metallireducens was the first iron-reducing organism isolated that coupled complete oxidation of organic acids with reduction of iron oxides (20,21). It completely oxidizes organic carbons such as fatty acids, alcohols, and monoaromatic compounds via the tricarboxylic acid (TCA) cycle (3, 20) coupled with the reduction of iron. The genomes of several Geobacter species have been sequenced, and proteome data are also available (5, 24). While the genome sequence and proteome are important for understanding Geobacter, they are not necessarily accurate represe...

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“…V (V) reduction was observed during field experiments at Old Rifle and has been shown to be mediated by iron reducing bacteria (Ortiz-Bernad et al, 2004). However, in these simulations we elected to ignore growth via V (V) reduction as there is considerable uncertainty in the chemical speciation of vanadium in groundwater at the Old Rifle site and this precluded our developing realistic growth equations for this process.…”

Section: Reaction Path Calculationsmentioning

confidence: 99%

Technical Report

Istok¹

2008

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PROJECT SUMMARY'Bioimmobilization' of redox-sensitive metals and radionuclides is being investigated as a way to remediate contaminated groundwater and sediments. In this approach, growth-limiting substrates are added to stimulate the activity of targeted groups of indigenous microorganisms and create conditions favorable for the microbially-mediated precipitation ('bioimmobilization') of targeted contaminants. This project investigated a fundamentally new approach for modeling this process that couples thermodynamic descriptions for microbial growth with associated geochemical reactions. In this approach, a synthetic microbial community is defined as a collection of defined microbial groups; each with a growth equation derived from bioenergetic principles. The growth equations and standard-state free energy yields are appended to a thermodynamic database for geochemical reactions and the combined equations are solved simultaneously to predict the effect of added substrates on microbial biomass, community composition, and system geochemistry. This approach, with a single set of thermodynamic parameters (one for each growth equation), was used to predict the results of laboratory and field bioimmobilization experiments at two geochemically diverse research sites. Predicted effects of ethanol or acetate addition on uranium and technetium solubility, major ion geochemistry, mineralogy, microbial biomass and community composition were in general agreement with experimental observations although the available experimental data precluded rigorous model testing. Model simulations provide insight into the long-standing difficulty in transferring experimental results from the laboratory to the field and from one field site to the next, especially if the form, concentration, or delivery of growth substrate is varied from one experiment to the next. Although originally developed for use in better understanding bioimmobilization of uranium and technetium via reductive precipitation, the modeling approach is potentially useful 3 for exploring the coupling of microbial growth and geochemical reactions in a variety of basic and applied biotechnology research settings. 4 INTRODUCTIONThe oxidized and mobile forms of uranium and technetium (such as uranyl carbonates or pertechnetate) have been shown to undergo microbially-mediated reductive transformations that result in the formation of less soluble products that are also less mobile in the environment. For example, certain anaerobic bacteria can enzymatically reduce U (VI) to U (IV) , which is essentially insoluble and, when sorbed, aggregated into large particles, or deposited onto sediment mineral phases, is also immobile (e.g., Lovley et al., 1993). Similarly, by stimulating the bio-reduction of technetium, it is possible to decrease aqueous concentrations of the mobile pertechnetate ion (Tc (VII) O 4 -) by forming insoluble and immobile Tc (IV) -oxides or sulfides (e.g., Wildung et al., 2000). Thus, by stimulating targeted indigenous microbial activities, aqueous con...

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Vanadium Respiration by Geobacter metallireducens : Novel Strategy for In Situ Removal of Vanadium from Groundwater

Cited by 213 publications

References 27 publications

Molecular analysis of phosphate limitation in Geobacteraceae during the bioremediation of a uranium-contaminated aquifer

Molecular analysis of phosphate limitation in Geobacteraceae during the bioremediation of a uranium-contaminated aquifer

Flux Analysis of Central Metabolic Pathways in Geobacter metallireducens during Reduction of Soluble Fe(III)-Nitrilotriacetic Acid

Technical Report

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