Two new arsenate/sulfate-reducing bacteria: mechanisms of arsenate reduction

Macy, Joan M.; Santini, Joanne M.; Pauling, B. V.; O’Neill, A. H.; Sly, Lindsay I.

doi:10.1007/s002030050007

Cited by 202 publications

(117 citation statements)

References 39 publications

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“…2: b-c). It is consistent with the previously observed simultaneous reduction of SO 4 2− and As (V) (Macy et al, 2000) or Fe(III) and As(V) (Smeaton et al, 2012), in which As is reduced as part of a detoxification pathway. Furthermore, the suggested detoxification mechanism may explain the bioreduction of other potentially toxic elements, for example U(VI), which can be reduced alongside of Fe(III) or SO 4 2− in sediments (Finneran et al, 2002;Komlos et al, 2008).…”

Section: Respiration Versus Detoxificationsupporting

confidence: 93%

Speciation dynamics of oxyanion contaminants (As, Sb, Cr) in argillaceous suspensions during oxic-anoxic cycles

Markelova

Couture

Parsons

et al. 2018

Applied Geochemistry

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A B S T R A C TArgillaceous geological formations are considered promising repositories for waste containing inorganic contaminants. However, the sequestration capacity of an argillaceous natural barrier may change as a result of dynamic environmental conditions, in particular changes in redox state. Here, we imposed redox cycles to argillaceous suspensions amended with a mixture of the inorganic contaminants As(V), Sb(V), Cr(VI), by alternating 7-day cycles of sparging with either oxic or anoxic gas mixtures. During the redox cycles, we assessed the relative importance of different contaminant sequestration mechanisms under sterile and non-sterile conditions. The non-sterile experiments were carried out 1) with the argillaceous material as is, that is, containing the native microbial population, 2) with the addition of ethanol as a source of labile organic carbon, and 3) with the addition of both ethanol and a soil microbial inoculum. In order to capture the observed solid-solution partitioning trends, a series of mixed thermodynamic-kinetic models representing the dynamic conditions in the experiments were developed using PHREEQC. Parameter values for processes such as adsorption, which occurred in all experiments, were kept constant across all the simulations. Additional formulations were introduced as needed to account for the microbial detoxification and respiration of the contaminants in the increasing complexity experiments. Abiotic adsorption of As and abiotic reductive precipitation of Cr dominated sequestration of these two contaminants under all experimental conditions, whereas the presence of microorganisms was essential to decrease the aqueous Sb concentration. Once reduced, As(III), Sb(III), and Cr(III) were not reoxidized upon exposure to dissolved O 2 in any of the experiments. Neither the mineralogy nor the native microbiota catalysed contaminant oxidation processes. Thus, kinetically, the reduction of As(V), Sb(V), and Cr(VI) was irreversible over the experimental duration (49 days). The capacity of the argillaceous matrix to reduce and sequester the aqueous contaminants, without subsequent remobilization to the aqueous phase during the oxic periods, supports the use of argillaceous barriers for geologic waste storage.

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Section: Respiration Versus Detoxificationsupporting

confidence: 93%

Speciation dynamics of oxyanion contaminants (As, Sb, Cr) in argillaceous suspensions during oxic-anoxic cycles

Markelova

Couture

Parsons

et al. 2018

Applied Geochemistry

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“…1c and 2c); this suggested that the SRB is only a part of the As(V)-reducing bacteria in the paddy soil. It was also previously shown that some of the SRB species have the ability of dissimilatory respiration of As(V) (Newman et al 1997;Macy et al 2000), suggesting that dissimilatory As(V) reduction also occurs in the sulfidogenic zone. Saalfield and Bostick (2009) suggest that bacterial reduction of As(V) is necessary for As sequestration in sulfides, even where sulfate reduction is active.…”

Section: Discussionmentioning

confidence: 78%

“…2). Most energy for microbes is generated from respiration supported by O 2 as the electron acceptor and under anaerobic conditions like flooded paddy soil, also by Fe(III), SO 4 2− , and As(V) etc., which is conducted by special microbial groups, and their activities determine the speciation and fate of elements in the environment (Newman et al 1997;Macy et al 2000;Lovley and Coats 2000;Saalfield and Bostick 2009). A stable community of SRB was obtained using enrichment culture method by SO 4 2− enrichment for 15 transfers and was also suggested to use the As(V) and Fe(III) as the electron acceptor under anaerobic soil conditions (Fig.…”

Section: Discussionmentioning

confidence: 99%

Arsenic bioavailability to rice plant in paddy soil: influence of microbial sulfate reduction

2015

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Purpose High arsenic (As) mobility in anaerobic paddy soil due to microbial Fe-and As-reducing processes results in As accumulation into rice plants. Sulfur (S) also undergoes microbial reducing processes in the anaerobic paddy soil, while this process interacts with the Fe-and As-reducing processes, forms secondary minerals, and thus influences As mobility in paddy soil. This work was carried out to investigate the role of sulfur and sulfate-reducing bacteria (SRB) in As redox transformation and bioavailability to rice plant in an anaerobic paddy soil. Materials and methods Anaerobic incubation experiments with or without sulfate (SO 4 2− ) and SRB were carried out to monitor S and iron (Fe) dynamics and their relations to As speciation and release to soil solution. Rice cultivation in pot experiment was then carried out to check the SO 4 2− amendment in bioavailability and uptake into rice plants.Results and discussion The inoculation of an enriched SRB community into the sterilized paddy soil increased reduction and release of As to the soil solution after flooding, showing its ability in arsenate (As(V)) as well as SO 4 2− reduction to arsenite (As(III)) and sulfide (S 2− ), respectively. Sulfate addition (2 and 100 mM) into the anaerobic paddy soil increased the reduction of SO 4 2− and ferric iron (Fe 3+ ) and resulted to lower dissolved As in the soil solution, which limited As mobility in the paddy soil. Application of SO 4 2− (100 mg kg −1 ) into paddy soil finally decreased the concentration of dissolved As in the soil solution by 23.5 % and also decreased As content in rice roots and iron plaque by 22.6 and 30.5 %, respectively. Conclusions The results revealed the important role of sulfur and the SRB activity in As speciation and mobility in anaerobic paddy soil, implying a lower As bioavailability to rice plants under sulfur-enriched anaerobic paddy soil, and an efficient way to reduce As accumulation in rice plants by sulfur fertilization in paddy soils.

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“…Since then, many more microorganisms that can reduce As(V) to arsenite [H 3 AsO 3 , As(III)] have been discovered (5)(6)(7)(8), but a mechanistic understanding of this metabolism has lagged. To date, only three studies have described the biochemistry of arsenate respiration (5,9,10), and detailed biochemical analyses have not been performed. In part, the limitations of these studies can be attributed to the fact that the As(V)-respiring organisms being studied were not genetically tractable.…”

mentioning

confidence: 99%

Genetic identification of a respiratory arsenate reductase

Saltikov

Newman²

2003

Proc. Natl. Acad. Sci. U.S.A.

445

361

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For more than a decade, it has been recognized that arsenate [H2AsO4 1-; As(V)] can be used by microorganisms as a terminal electron acceptor in anaerobic respiration. Given the toxicity of arsenic, the mechanistic basis of this process is intriguing, as is its evolutionary origin. Here we show that a two-gene cluster (arrAB; arsenate respiratory reduction) in the bacterium Shewanella sp. strain ANA-3 specifically confers respiratory As(V) reductase activity. Mutants with in-frame deletions of either arrA or arrB are incapable of growing on As(V), yet both are able to grow on a wide variety of other electron acceptors as efficiently as the wild-type. Complementation by the wild-type sequence rescues the mutants' ability to respire As(V). arrA is predicted to encode a 95.2-kDa protein with sequence motifs similar to the molybdenum containing enzymes of the dimethyl sulfoxide reductase family. arrB is predicted to encode a 25.7-kDa iron-sulfur protein. arrA and arrB comprise an operon that contains a twin arginine translocation (Tat) motif in ArrA (but not in ArrB) as well as a putative anaerobic transcription factor binding site upstream of arrA, suggesting that the respiratory As(V) reductase is exported to the periplasm via the Tat pathway and under anaerobic transcriptional control. These genes appear to define a new class of reductases that are specific for respiratory As(V) reduction.T he consumption of arsenic (As)-tainted surface waters and ground waters has created a public health crisis in many countries (1, 2). Although much of the As contamination derives from natural weathering and dissolution of As-bearing minerals, recognition that microorganisms can alter the mobility of As in natural waters through redox transformations (3) drove the discovery of the first arsenate [As(V)]-respiring bacterium nearly a decade ago (4). Since then, many more microorganisms that can reduce As(V) to arsenite [H 3 AsO 3 , As(III)] have been discovered (5-8), but a mechanistic understanding of this metabolism has lagged. To date, only three studies have described the biochemistry of arsenate respiration (5, 9, 10), and detailed biochemical analyses have not been performed. In part, the limitations of these studies can be attributed to the fact that the As(V)-respiring organisms being studied were not genetically tractable. To quantify the geochemical impact of As(V)-respiring microorganisms in a given locale, we must be able to predict when these organisms will be active, and how rapidly they will transform As(V). Identification of the gene(s) that control this process, elucidation of their regulation, and determination of the kinetics of their protein products, are necessary steps toward understanding the specific contribution of As(V)-respiring bacteria to As-cycling in the environment.In response to this need, a new As(V)-respiring species, Shewanella strain ANA-3 that is amenable to genetic analysis, was recently isolated (8). This organism contains two systems for reducing As(V). One is similar to the well conserved...

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Two new arsenate/sulfate-reducing bacteria: mechanisms of arsenate reduction

Cited by 202 publications

References 39 publications

Speciation dynamics of oxyanion contaminants (As, Sb, Cr) in argillaceous suspensions during oxic-anoxic cycles

Speciation dynamics of oxyanion contaminants (As, Sb, Cr) in argillaceous suspensions during oxic-anoxic cycles

Arsenic bioavailability to rice plant in paddy soil: influence of microbial sulfate reduction

Genetic identification of a respiratory arsenate reductase

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