Characterization of the
            <i>ars</i>
            Gene Cluster from Extremely Arsenic-Resistant
            <i>Microbacterium</i>
            sp. Strain A33

Achour-Rokbani, Asma; Cordi, Audrey; Poupin, Pascal; Bauda, Pascale; Billard, Patrick

doi:10.1128/aem.01738-09

Cited by 69 publications

(45 citation statements)

References 43 publications

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“…Additionally, some ars operons contain an ArsB complexing As 3+ -translocating ATPase (ArsA), enhancing resistance [233], and an arsenic metallochaperone (ArsD) that transfers As 3+ to ArsA, increasing its ability to extrude arsenite [234,235]. Other genes associated with ars operons include the putative thioredoxin reductase (arsT) [236,237] or thioredoxin system (arsTX) [238] required for As(V) reduction using NADPH reducing power, and two genes of unknown function with weak homology to oxidoreductases (arsO and arsH) [236,239,240]. The ArsH protein from Shigella flexneri was shown to have NADPH-dependent FMN reductase activity [241].…”

Section: Other Metals (Arsenic Cadmium Nickel Uranium)mentioning

confidence: 99%

The Confluence of Heavy Metal Biooxidation and Heavy Metal Resistance: Implications for Bioleaching by Extreme Thermoacidophiles

et al. 2015

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Extreme thermoacidophiles (Topt > 65 °C, pHopt < 3.5) inhabit unique environments fraught with challenges, including extremely high temperatures, low pH, as well as high levels of soluble metal species. In fact, certain members of this group thrive by metabolizing heavy metals, creating a dynamic equilibrium between biooxidation to meet bioenergetic needs and mechanisms for tolerating and resisting the toxic effects of solubilized metals. Extremely thermoacidophilic archaea dominate bioleaching operations at elevated temperatures and have been considered for processing certain mineral types (e.g., chalcopyrite), some of which are recalcitrant to their mesophilic counterparts. A key issue to consider, in addition to temperature and pH, is the extent to which solid phase heavy metals are solubilized and the concomitant impact of these mobilized metals on the microorganism's growth physiology. Here, extreme thermoacidophiles are examined from the perspectives of biodiversity, heavy metal biooxidation, metal resistance mechanisms, microbe-solid interactions, and application of these archaea in biomining operations.

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Section: Other Metals (Arsenic Cadmium Nickel Uranium)mentioning

confidence: 99%

The Confluence of Heavy Metal Biooxidation and Heavy Metal Resistance: Implications for Bioleaching by Extreme Thermoacidophiles

et al. 2015

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“…Operon composition usually is comprised of at least arsR, arsC (encoding arsenate reductase), and either an arsB or acr3 gene [coding for different proteins involved in As(III) extrusion from the cytoplasm]. Depending on the organism, additional ars operon elements can include arsA, which codes for an ATPase that associates with ArsB, enabling the latter to use ATP to energize the extrusion of As(III) (4); arsD, coding for a protein that can exhibit weak repressor activity, but with a primary function currently viewed as arsenic metallochaperone activity (5-7); arsH, which was recently shown to encode an organoarsenical oxidase capable of oxidizing trivalent methylated and aromatic arsenicals (8); arsI, encoding an alternative As(V) reductase that differs from ArsC (9); another arsI gene, encoding a C-As lyase (10); arsO, encoding a putative flavin-binding monooxygenase (11); arsP, encoding a putative membrane permease (12,13); and arsTX, encoding a thioredoxin system transcribed along with an arsRC2 fusion gene (14). Gene duplication within these operons has been observed (15), as is the case with Agrobacterium tumefaciens 5A (Fig.…”

mentioning

confidence: 99%

Regulatory Activities of Four ArsR Proteins in Agrobacterium tumefaciens 5A

Kang

Brame

Jetter

et al. 2016

Appl Environ Microbiol

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ArsR is a well-studied transcriptional repressor that regulates microbe-arsenic interactions. Most microorganisms have an arsR gene, but in cases where multiple copies exist, the respective roles or potential functional overlap have not been explored. We examined the repressors encoded by arsR1 and arsR2 (ars1 operon) and by arsR3 and arsR4 (ars2 operon) in Agrobacterium tumefaciens 5A. ArsR1 and ArsR4 are very similar in their primary sequences and diverge phylogenetically from ArsR2 and ArsR3, which are also quite similar to one another. Reporter constructs (lacZ) for arsR1, arsR2, and arsR4 were all inducible by As(III), but expression of arsR3 (monitored by reverse transcriptase PCR) was not influenced by As(III) and appeared to be linked transcriptionally to an upstream lysR-type gene. Experiments using a combination of deletion mutations and additional reporter assays illustrated that the encoded repressors (i) are not all autoregulatory as is typically known for ArsR proteins, (ii) exhibit variable control of each other's encoding genes, and (iii) exert variable control of other genes previously shown to be under the control of ArsR1. Furthermore, ArsR2, ArsR3, and ArsR4 appear to have an activator-like function for some genes otherwise repressed by ArsR1, which deviates from the well-studied repressor role of ArsR proteins. The differential regulatory activities suggest a complex regulatory network not previously observed in ArsR studies. The results indicate that fine-scale ArsR sequence deviations of the reiterated regulatory proteins apparently translate to different regulatory roles. IMPORTANCEGiven the significance of the ArsR repressor in regulating various aspects of microbe-arsenic interactions, it is important to assess potential regulatory overlap and/or interference when a microorganism carries multiple copies of arsR. This study explores this issue and shows that the four arsR genes in A. tumefaciens 5A, associated with two separate ars operons, encode proteins exhibiting various degrees of functional overlap with respect to autoregulation and cross-regulation, as well as control of other functional genes. In some cases, differences in regulatory activity are associated with only limited differences in protein primary structure. The experiments summarized herein also present evidence that ArsR proteins appear to have activator functions, representing novel regulatory activities for ArsR, previously known only to be a repressor. In reaction to arsenic in their environment, microorganisms orchestrate an organized response that may involve arsenite [As(III)] oxidation, arsenate [As(V)] reduction, or both. These redox reactions serve to detoxify or protect the organism or to generate energy, depending on the organism and the genes involved. Current models depict As(III) being taken up into the cell via aquaglyceroporins (e.g., reviewed in references 1, 2, and 3), where it then interacts with a DNA-binding repressor protein, ArsR, resulting in a conformational change in ArsR and causing it...

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“…The most arsenic-resistant species have been shown to rely on typical detoxification genes, chromosomally encoded but organized in unique ways: Microbacterium sp. strain A33 encodes an operon containing three arsenate reductases, one of which is fused to an arsRlike gene (Achour-Rokbani et al, 2010); Ochrobactrum tritici and Corynebacterium glutamicum have two structurally different chromosomal operons encoding arsenic-resistance genes (Branco et al, 2008;Ordó ñez et al, 2005); and Desulfovibrio desulfuricans possesses an arsRBCC operon and one arsC coding gene located in a separate chromosomal region (Li & Krumholz, 2007). These bacteria display levels of arsenate resistance ranging from 50 mM (D. desulfuricans) to 800 mM (Microbacterium sp.…”

Section: Discussionmentioning

confidence: 99%

Arsenate reduction and expression of multiple chromosomal ars operons in Geobacillus kaustophilus A1

et al. 2011

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Geobacillus kaustophilus strain A1 was previously isolated from a geothermal environment for its ability to grow in the presence of high arsenate levels. In this study, the molecular mechanisms of arsenate resistance of the strain were investigated. As(V) was reduced to As(III), as shown by HPLC analysis. Consistent with the observation that the micro-organism is not capable of anaerobic growth, no respiratory arsenate reductases were identified. Using specific PCR primers based on the genome sequence of G. kaustophilus HTA426, three unlinked genes encoding detoxifying arsenate reductases were detected in strain A1. These genes were designated arsC1, arsC2 and arsC3. While arsC3 is a monocistronic locus, sequencing of the regions flanking arsC1 and arsC2 revealed the presence of additional genes encoding a putative arsenite transporter and an ArsR-like regulator upstream of each arsenate reductase, indicating the presence of sequences with putative roles in As(V) reduction, As(III) export and arsenic-responsive regulation. RT-PCR demonstrated that both sets of genes were co-transcribed. Furthermore, arsC1 and arsC2, monitored by quantitative real-time RT-PCR, were upregulated in response to As(V), while arsC3 was constitutively expressed at a low level. A mechanism for regulation of As(V) detoxification by Geobacillus that is both consistent with our findings and relevant to the biogeochemical cycle of arsenic and its mobility in the environment is proposed. INTRODUCTIONMicro-organisms have an important impact on the biogeochemical transformations of arsenic, and their activities affect the mobility and toxicity of this element. Elevated amounts of arsenic can occur, especially in geothermal environments (Stauffer & Thompson, 1984). Thus, thermophilic micro-organisms such as Geobacillus species that thrive in geothermal soils and sediments are of particular interest for studying the mechanisms for the detoxification of arsenic compounds.Genes for arsenic detoxification were first discovered and characterized in Gram-negative bacteria (Chen et al., 1986;Rosen, 1999). These genes are often plasmid-encoded and are widespread in prokaryotes (Bruhn et al., 1996;Ji & Silver, 1992b;Oden et al., 1994;Rosenstein et al., 1992). In thoroughly studied systems, the ars operon has been reported to contain the five genes arsRDABC, as in Escherichia coli (Cai & DuBow, 1996;Rosen et al., 1992), or at least the three genes arsRBC, as in Staphylococcus aureus (Silver et al., 1993). ArsA and ArsB are components of an arsenite-transporting ATPase, where ArsA is the ATPase and ArsB is the transmembrane component of the complex. In micro-organisms in which ArsA is absent, ArsB acts as a single-component transporter. Both ArsA and ArsB may confer resistance to arsenite and antimonite (Rosen, 1999). In its dimeric form, ArsR is an arsenite-responsive repressor that binds to the ars promoter (Xu & Rosen, 1997). ArsC is the arsenate reductase that converts arsenate to arsenite, conferring resistance to arsenate (Martin et al., 2001 Here w...

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Characterization of the ars Gene Cluster from Extremely Arsenic-Resistant Microbacterium sp. Strain A33

Cited by 69 publications

References 43 publications

The Confluence of Heavy Metal Biooxidation and Heavy Metal Resistance: Implications for Bioleaching by Extreme Thermoacidophiles

The Confluence of Heavy Metal Biooxidation and Heavy Metal Resistance: Implications for Bioleaching by Extreme Thermoacidophiles

Regulatory Activities of Four ArsR Proteins in Agrobacterium tumefaciens 5A

Arsenate reduction and expression of multiple chromosomal ars operons in Geobacillus kaustophilus A1

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