The respiratory arsenate reductase from<i>Bacillus selenitireducens</i>strain MLS10

Afkar, Eman; Lisak, Joy; Saltikov, Chad W.; Basu, Partha; Oremland, Ronald S.; Stolz, John F.

doi:10.1016/s0378-1097(03)00609-8

Cited by 177 publications

(113 citation statements)

References 34 publications

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“…Saltikov encode components of a respiratory As(V) reductase. Biochemical and molecular data emerging from studies of the haloalkaliphilic As(V) respiring bacterium B. selenitireducens strain MLS10, also suggest that ArrA and ArrB homologs are present in this strain (24). These organisms are only very distantly related to each other, representing three distinct phyla within the Bacteria (27): Shewanella ANA-3 (8) is a member of the ␥-subgroup of the Proteobacteria, C. arsenatis (28) is considered the type species for the Chrysiogenetes, whereas D. hafniense (29) and B. selenitireducens (30) both represent the phylum Firmicutes.…”

Section: Discussionmentioning

confidence: 93%

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Genetic identification of a respiratory arsenate reductase

Saltikov

Newman²

2003

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

431

355

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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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Section: Discussionmentioning

confidence: 93%

“…ArrA clusters most closely with a hypothetical protein from the As(V)-respiring bacterium Desulfitobacterium hafniense (Desu0744; 51% amino acid identity, 68% amino acid similarity) and a putative arsenate reductase from Bacillus selenitireducens (ref. 24; 46% amino acid identity, 63% amino acid similarity). Fig.…”

Section: Resultsmentioning

confidence: 99%

Genetic identification of a respiratory arsenate reductase

Saltikov

Newman²

2003

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

431

355

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“…In contrast, As(V)-reductases (ArrA, ArrB, etc.) reside interior to the outer membrane-within the periplasm for Gram (-) bacteria (Afkar et al, 2003;Oremland and Stolz, 2003;.…”

Section: Arsenate Reduction: Detoxificationmentioning

confidence: 99%

Arsenic Chemistry in Soils and Sediments

Fendorf

Nico

Kocar

et al. 2010

Synchrotron-Based Techniques in Soils and Sediments

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“…Dissimilatory As(V) reduction has also been documented to occur in numerous prokaryotes in both prokaryotic domains (38), although its original discovery was more recent (2), and as a consequence, far less is known about the genetic determinants required for anaerobic As(V) respiration. Dissimilatory As(V) reductases from Chrysiogenes arsenatis (25) and Bacillus selenitireducens (1) have been purified and characterized, and the arr genes have been identified in Shewanella sp. strain ANA-3 (45).…”

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confidence: 99%

A Na ⁺ :H ⁺ Antiporter and a Molybdate Transporter Are Essential for Arsenite Oxidation in Agrobacterium tumefaciens

et al. 2006

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Transposon Tn5-B22 mutagenesis was used to identify genetic determinants required for arsenite [As(III)] oxidation in an Agrobacterium tumefaciens soil isolate, strain 5A. In one mutant, the transposon interrupted modB, which codes for the permease component of a high-affinity molybdate transporter. In a second mutant, the transposon insertion occurred in mrpB, which is part of a seven-gene operon encoding an Mrp-type Na ؉ :H ؉ antiporter complex. Complementation experiments with mod and mrp operons PCR cloned from the genomesequenced A. tumefaciens strain C58 resulted in complementation back to an As(III)-oxidizing phenotype, confirming that these genes encode activities essential for As(III) oxidation in this strain of A. tumefaciens. As expected, the mrp mutant was extremely sensitive to NaCl and LiCl, indicating that the Mrp complex in A. tumefaciens is involved in Na ؉ circulation across the membrane. Gene expression studies (lacZ reporter and reverse transcriptase PCR experiments) failed to show evidence of transcriptional regulation of the mrp operon in response to As(III) exposure, whereas expression of the mod operon was found to be up-regulated by As(III) exposure. In each mutant, the loss of As(III)-oxidizing capacity resulted in conversion to an arsenate [As(V)]-reducing phenotype. Neither mutant was more sensitive to As(III) than the parental strain.Microbe-arsenic interactions are viewed as a major driver of arsenic (As) chemical speciation in nature, which in turn is a critical factor in determining As fate and transport in the environment (reviewed in references 19 and 38). Many types of As transformations have been documented in various microorganisms (6,14,18,34,41,47), although those currently seen to dominate As speciation in the environment involve either arsenite [H 3 AsO 3 , As(III)] oxidation or arsenate [HAsO 4 2Ϫ , As(V)] reduction. These redox transformation reactions are generally thought to be used by microorganisms either for detoxification or for generating cellular energy to support growth (see reviews in references 19, 38, 49 and 50).Detoxification-based As(V) reduction has been documented to occur in microorganisms throughout the domains Bacteria and Archaea (38, 49), and involves As(V) reduction to As(III) via an As(V) reductase, with the As(III) then extruded by the ArsB efflux pump that is efficient at removing As(III) and antimonite [Sb(III)]. This process, as well as the genes encoding the enzymes and regulatory proteins involved, has been extensively studied and recently reviewed by Silver and Phung (49). Dissimilatory As(V) reduction has also been documented to occur in numerous prokaryotes in both prokaryotic domains (38), although its original discovery was more recent (2), and as a consequence, far less is known about the genetic determinants required for anaerobic As(V) respiration. Dissimilatory As(V) reductases from Chrysiogenes arsenatis (25) and Bacillus selenitireducens (1) have been purified and characterized, and the arr genes have been identified in Shewanella...

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The respiratory arsenate reductase fromBacillus selenitireducensstrain MLS10

Cited by 177 publications

References 34 publications

Genetic identification of a respiratory arsenate reductase

Genetic identification of a respiratory arsenate reductase

Arsenic Chemistry in Soils and Sediments

A Na ⁺ :H ⁺ Antiporter and a Molybdate Transporter Are Essential for Arsenite Oxidation in Agrobacterium tumefaciens

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The respiratory arsenate reductase fromBacillus selenitireducensstrain MLS10

Cited by 177 publications

References 34 publications

Genetic identification of a respiratory arsenate reductase

Genetic identification of a respiratory arsenate reductase

Arsenic Chemistry in Soils and Sediments

A Na + :H + Antiporter and a Molybdate Transporter Are Essential for Arsenite Oxidation in Agrobacterium tumefaciens

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A Na ⁺ :H ⁺ Antiporter and a Molybdate Transporter Are Essential for Arsenite Oxidation in Agrobacterium tumefaciens