Humic Substances as a Mediator for Microbially Catalyzed Metal Reduction

Lovley, Derek R.; Fraga, J. L.; Blunt-Harris, Elizabeth L.; Hayes, Lory A.; Phillips, Elizabeth; Coates, John D.

doi:10.1002/(sici)1521-401x(199805)26:3<152::aid-aheh152>3.0.co;2-d

Cited by 442 publications

(302 citation statements)

References 25 publications

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“…Bioavailable organic matter as an electron reservoir constitutes the bulk of the soil's reduction capacity (Chadwick and Chorover 2001;Lovley et al 1998). Organic matter can be partly, and reversibly, reduced by microorganisms, and it plays the role of electron shuttle, i.e.…”

Section: Soil Eh and Ph And Soil Organic Mattermentioning

confidence: 99%

Redox potential (Eh) and pH as drivers of soil/plant/microorganism systems: a transdisciplinary overview pointing to integrative opportunities for agronomy

2012

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Background Oxidation-reduction and acid-base reactions are essential for the maintenance of all living organisms. However, redox potential (Eh) has received little attention in agronomy, unlike pH, which is regarded as a master variable. Agronomists are probably depriving themselves of a key factor in crop and soil science which could be a useful integrative tool. Scope This paper reviews the existing literature on Eh in various disciplines connected to agronomy, whether associated or not with pH, and then integrates this knowledge within a composite framework. Conclusions This transdisciplinary review offers evidence that Eh and pH are respectively and jointly major drivers of soil/plant/microorganism systems. Information on the roles of Eh and pH in plant and microorganism physiology and in soil genesis converges to form an operational framework for further studies of soil/plant/microorganism functioning. This framework is based on the hypothesis that plants physiologically function within a specific internal Eh-pH range and that, along with microorganisms, they alter Eh and pH in the rhizosphere to ensure homeostasis at the cell level. This new perspective could help in bridging several disciplines related to agronomy, and across micro and macro-scales. It should help to improve cropping systems design and management, in conventional, organic, and conservation agriculture.

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Section: Soil Eh and Ph And Soil Organic Mattermentioning

confidence: 99%

Redox potential (Eh) and pH as drivers of soil/plant/microorganism systems: a transdisciplinary overview pointing to integrative opportunities for agronomy

2012

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“…As known, the microorganisms with the capacity to conserve energy from humus reduction are phylogenetically dispersed, the most representative strains are Desulfuromonas acetexigens (Lovley et al 1998), Corynebacterium humireducens sp. nov (Wu et al 2010), and Geobacter metallireducens (Lovley et al 1996b).…”

Section: Effect Of Electron Donors On Aqds Reduction By Strain Pah-1mentioning

confidence: 99%

Anaerobic degradation of phenanthrene by a newly isolated humus-reducing bacterium, Pseudomonas aeruginosa strain PAH-1

Wang

et al. 2011

J Soils Sediments

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Purpose The anaerobic degradation of polycyclic aromatic hydrocarbons (PAHs) has great significance to PAHs' natural attenuation in contaminated sites. Previous studies mainly focused on anaerobic PAH degradation by mixed cultures with nitrate, sulfate, or Fe(III) oxides as electron acceptors, and the roles of pure cultures in the process was rarely reported. The aim of this paper is to isolate a pure culture that is capable of degrading phenanthrene anaerobically with anthraquinone-2,6-disulphonate (AQDS) as the sole electron acceptor and evaluate its environmental functions. Materials and methods A strain of pure culture was isolated from anodic solution of a microbial fuel cell via enrichment procedure with phenanthrene and AQDS under anaerobic conditions. Using the single colony isolation technique, a distinct colony was obtained and identified by the phenotypic and phylogenetic analysis. Its ability to reduce AQDS and degrade phenanthrene was conducted in serum bottles by standard anaerobic techniques (purged with 80% N 2 −20% CO 2 ). The concentration of AH 2 QDS and fructose was quantified by UV-vis spectrophotometer at 450 and 210 nm, respectively. Cells number was determined by direct plate counting on aerobic LB agar medium. The concentration of phenanthrene was determined using HPLC. Results and discussion Strain PAH-1 was identified as Pseudomonas aeruginosa. It could oxidize fructose or glucose to reduce AQDS and can support microbial growth by conserving energy from fructose to AQDS. It has the ability to degrade phenanthrene directly with AQDS as the sole electron acceptor (46.5% removal), and the microbial process may be AQDS dependent. The addition of small organic substances (fructose) could enhance the anaerobic biodegradation of phenanthrene from 46.5% to 56.7%. The anaerobic degradation of phenanthrene fits the pseudo-firstorder kinetics, giving the rate constants of 0.0233/day (R 2 =0.934) and 0.0328/day (R 2 =0.933) for non-fructose set and fructose set, respectively. Conclusions We successfully isolated a facultative anaerobe, P. aeruginosa strain PAH-1. This study was the first paper reporting that a pure culture (strain PAH-1) has the ability to anaerobically degrade phenanthrene with AQDS as the sole electron acceptor. The finding also explores the environmental significance of the Pseudomonas genus.

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“…In fact, many studies have shown that EES increased iron reduction under various conditions. For example, Lovley et al (1998) reported that humic substances as EES stimulated the reduction of structural Fe(III) in clay, poorly crystalline Fe(III) hydroxides, and crystalline Fe(III) (hydr)oxides (i.e., goethite and hematite) . A recent study also showed that the presence of anthraquinone-2,6-disulfonate (AQDS) enhanced the microbial reduction of iron oxides more than 15 times with xylose as a carbon source (Gerlach et al, 2011).…”

Section: Extracellular Electron Shuttles (Ees) Have Been Proposedmentioning

confidence: 99%

Effects of Extracellular Electron Shuttles on Microbial Iron Reduction and Heavy Metals Release from Contaminated Soils

Hwang¹,

Shim²,

Oh³

et al. 2014

Journal of Soil and Groundwater Environment

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To test the potential effects of extracellular electron shuttles (EES) on the rate and extent of heavy metal release from contaminated soils during microbial iron reduction, we created anaerobic batch systems with anthraquinone-2,6-disulfonate (AQDS) as a surrogate of EES, and with contaminated soils as mixed iron (hydr)oxides and microbial sources.Two types of soils were tested: Zn-contaminated soil A and As/Pb-contaminated soil B. In soil A, the rate of iron reduction was fastest in the presence of AQDS and > 3500 mg/L of total Fe(II) was produced within 2 d. This suggests that indigenous microorganisms can utilize AQDS as EES to stimulate iron reduction. In the incubations with soil B, the rate and extent of iron reduction did not increase in the presence of AQDS likely because of the low pH (< 5.5). In addition, less than 2000 mg/L of total Fe(II) was produced in soil B within 52 d suggesting that iron reduction by subsurface microorganisms in soil B was not as effective as that in soil A. Relatively high amount of As (~500 mg/L) was released to the aqueous phase during microbial iron reduction in soil B. The release of As might be due to the reduction of As-associated iron (hydr)oxides and/or direct enzymatic reduction of As(V) to As(III) by As-reducing microorganisms. However, given that Pb in liquid phase was < 0.3 mg/L for the entire experiment, the microbial reduction As(V) to As(III) by As-reducing microorganisms has most likely occurred in this system. This study suggests that heavy metal release from contaminated soils can be strongly controlled by subsurface microorganisms, soil pH, presence of EES, and/or nature of heavy metals.

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Humic Substances as a Mediator for Microbially Catalyzed Metal Reduction

Cited by 442 publications

References 25 publications

Redox potential (Eh) and pH as drivers of soil/plant/microorganism systems: a transdisciplinary overview pointing to integrative opportunities for agronomy

Redox potential (Eh) and pH as drivers of soil/plant/microorganism systems: a transdisciplinary overview pointing to integrative opportunities for agronomy

Anaerobic degradation of phenanthrene by a newly isolated humus-reducing bacterium, Pseudomonas aeruginosa strain PAH-1

Effects of Extracellular Electron Shuttles on Microbial Iron Reduction and Heavy Metals Release from Contaminated Soils

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