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Abstract
Since the original report that Halomonas sp. strain GFAJ-1 was capable of using arsenic instead of phosphorus to sustain growth, additional studies have been conducted, and GFAJ-1 is now considered a highly arsenic-resistant but phosphorus-dependent bacterium. However, the mechanisms supporting the extreme arsenic resistance of the GFAJ-1 strain remain unknown. In this study, we show that GFAJ-1 has multiple distinct arsenic resistance mechanisms. It lacks the genes to reduce arsenate, which is the essential step in the well-characterized resistance mechanism of arsenate reduction coupled to arsenite extrusion. Instead, GFAJ-1 has two arsenic resistance operons, arsH1-acr3-2-arsH2 and mfs1-mfs2-gapdh, enabling tolerance to high levels of arsenate. mfs2 and gapdh encode proteins homologous to Pseudomonas aeruginosa ArsJ and glyceraldehyde-3-phosphate dehydrogenase (GAPDH), respectively, which constitute the equivalent of an As(V) efflux system to catalyze the transformation of inorganic arsenate to pentavalent organoarsenical 1-arseno-3-phosphoglycerate and its subsequent extrusion. Surprisingly, the arsH1-acr3-2-arsH2 operon seems to consist of typical arsenite resistance genes, but this operon is sufficient to confer both arsenite and arsenate resistance on Escherichia coli AW3110 even in the absence of arsenate reductase, suggesting a novel pathway of arsenic detoxification. The simultaneous occurrence of these two unusual detoxification mechanisms enables the adaptation of strain GFAJ-1 to the particularly arsenic-rich environment of Mono Lake. Halomonas sp. strain GFAJ-1 was previously reported to use arsenic as a substitute for phosphorus to sustain life under phosphate-limited conditions. Although this claim was later undermined by several groups, how GFAJ-1 can thrive in environments with high arsenic concentrations remains unclear. Here, we determined that this ability can be attributed to the possession of two arsenic detoxification operons, arsH1-acr3-2-arsH2 and mfs1-mfs2-gapdh. mfs2 and gapdh encode proteins homologous to ArsJ and GAPDH in Pseudomonas aeruginosa; these proteins create an arsenate efflux pathway to reduce cellular arsenate accumulation. Interestingly, the combination of acr3-2 with either arsH gene was sufficient to confer resistance to both arsenite and arsenate in E. coli AW3110, even in the absence of arsenate reductase, suggesting a new strategy for bacterial arsenic detoxification. This study concludes that the survival of GFAJ-1 in high arsenic concentrations is attributable to the cooccurrence of these two unusual arsenic detoxification mechanisms.
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102
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Li Y, Jiang M, Thunders M, Ai X, Qiu J. Effect of enrofloxacin and roxarsone on CYP450s in pig. Res Vet Sci 2018; 117:97-98. [DOI: 10.1016/j.rvsc.2017.11.014] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2017] [Revised: 11/02/2017] [Accepted: 11/18/2017] [Indexed: 11/30/2022]
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103
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Draft Genome Sequence of Pseudomonas gingeri Strain LMG 5327, the Causative Agent of Ginger Blotch in Agaricus bisporus. GENOME ANNOUNCEMENTS 2018; 6:6/13/e00196-18. [PMID: 29599158 PMCID: PMC5876480 DOI: 10.1128/genomea.00196-18] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The draft genome sequence of Pseudomonas gingeri LMG 5327 (NCPPB 3146), the causative agent of ginger blotch in Agaricus bisporus, is reported. Together with another mushroom pathogen, Pseudomonas agarici, it belongs to a distinct phylogenomic group.
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104
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Chang JS, Yoon IH, Kim KW. Arsenic biotransformation potential of microbial arsH responses in the biogeochemical cycling of arsenic-contaminated groundwater. CHEMOSPHERE 2018; 191:729-737. [PMID: 29080535 DOI: 10.1016/j.chemosphere.2017.10.044] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/09/2017] [Revised: 10/05/2017] [Accepted: 10/07/2017] [Indexed: 06/07/2023]
Abstract
ArsH encodes an oxidoreductase, an NAD(P)H-dependent mononucleotide reductase, with an unknown function, frequently within an ars operon, and is widely distributed in bacteria. Novel arsenite-oxidizing bacteria have been isolated from arsenic-contaminated groundwater and surface soil in Vietnam. We found that ArsH gene activity, with arsenite oxidase in the periplasm; it revealed arsenic oxidation potential of the arsH system. Batch experiment results revealed Citrobacter freundii strain VTan4 (DQ481466) and Pseudomonas putida strain VTw33 (DQ481482) completely oxidized 1 mM of arsenite to arsenate within 30-50 h. High concentrations of arsenic were detected in groundwater and surrounding soil obtained from Vinh Tru village in Ha Nam province (groundwater: 11.0 μg/L to 37.0 μg/L; and soil: 2.5 mg/kg, 390.1 mg/kg), respectively. An arsH gene encoding an organoarsenical oxidase protein was observed in arsenite-oxidizing Citrobacter freundii strain VTan4 (DQ481466), whereas arsB, arsH, and arsH were detected in Pseudomonas putida strain VTw33 (DQ481482). arsH gene in bacteria was first reported from Vietnam for resistance and arsenite oxidase. We proposed that residues, Ser 43, Arg 45, Ser 48, and Tyr 49 are required for arsenic binding and activation of arsH. The ars-mediated biotransformation strongly influenced potential arsenite oxidase enzyme of the operon encoding a homogeneous arsH. Results suggest that the further study of arsenite-oxidizing bacteria may lead to a better understanding of arsenite oxidase responses, such as those of arsH, that may be applied to control biochemical properties; for example, speciation, detoxification, bioremediation, biotransformation, and mobilization of arsenic in contaminated groundwater.
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Affiliation(s)
- Jin-Soo Chang
- Molecular Biogeochemistry Laboratory, Biological & Genetic Resources Institute (BGRI), Hannam University (Jeonmin Campus), 505 Inno-Biz Park, 1646 Yuseong-daero, Yeseong-gu, Daejeon, 34054, Republic of Korea
| | - In-Ho Yoon
- Decommissioning Technology Research Division, Korea Atomic Energy Research Institute (KAERI), 111 Daedeok-daero, 989 Beon-gil, Yuseong-gu, Daejeon, 34057, Republic of Korea
| | - Kyoung-Woong Kim
- School of Earth Sciences and Environmental Engineering, Gwangju Institute of Science and Technology (GIST), 261 Cheomdan-gwagiro, Buk-gu, Gwangju, 61005, Republic of Korea.
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105
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Li J, Pawitwar SS, Rosen BP. The organoarsenical biocycle and the primordial antibiotic methylarsenite. Metallomics 2017; 8:1047-1055. [PMID: 27730229 DOI: 10.1039/c6mt00168h] [Citation(s) in RCA: 49] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Arsenic is the most pervasive environmental toxic substance. As a consequence of its ubiquity, nearly every organism has genes for resistance to inorganic arsenic. In bacteria these genes are found largely in bacterial arsenic resistance (ars) operons. Recently a parallel pathway for synthesis and degradation of methylated arsenicals has been identified. The arsM gene product encodes the ArsM (AS3MT in animals) As(iii) S-adenosylmethionine methyltransferase that methylates inorganic trivalent arsenite in three sequential steps to methylarsenite MAs(iii), dimethylarsenite (DMAs(iii) and trimethylarsenite (TMAs(iii)). MAs(iii) is considerably more toxic than As(iii), and we have proposed that MAs(iii) was a primordial antibiotic. Under aerobic conditions these products are oxidized to nontoxic pentavalent arsenicals, so that methylation became a detoxifying pathway after the atmosphere became oxidizing. Other microbes have acquired the ability to regenerate MAs(v) by reduction, transforming it again into toxic MAs(iii). Under this environmental pressure, MAs(iii) resistances evolved, including the arsI, arsH and arsP genes. ArsI is a C-As bond lyase that demethylates MAs(iii) back to less toxic As(iii). ArsH re-oxidizes MAs(iii) to MAs(v). ArsP actively extrudes MAs(iii) from cells. These proteins confer resistance to this primitive antibiotic. This oscillation between MAs(iii) synthesis and detoxification is an essential component of the arsenic biogeocycle.
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Affiliation(s)
- Jiaojiao Li
- Department of Cellular Biology and Pharmacology, Herbert Wertheim College of Medicine, Florida International University, 11200 S.W. 8 Street, Miami, FL 33199 USA
| | - Shashank S Pawitwar
- Department of Cellular Biology and Pharmacology, Herbert Wertheim College of Medicine, Florida International University, 11200 S.W. 8 Street, Miami, FL 33199 USA
| | - Barry P Rosen
- Department of Cellular Biology and Pharmacology, Herbert Wertheim College of Medicine, Florida International University, 11200 S.W. 8 Street, Miami, FL 33199 USA
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106
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Chen J, Nadar VS, Rosen BP. A novel MAs(III)-selective ArsR transcriptional repressor. Mol Microbiol 2017; 106:469-478. [PMID: 28861914 DOI: 10.1111/mmi.13826] [Citation(s) in RCA: 36] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/28/2017] [Indexed: 11/29/2022]
Abstract
Microbial expression of genes for resistance to heavy metals and metalloids is usually transcriptionally regulated by the toxic ions themselves. Arsenic is a ubiquitous, naturally occurring toxic metalloid widely distributed in soil and groundwater. Microbes biotransform both arsenate (As(V)) and arsenite (As(III)) into more toxic methylated metabolites methylarsenite (MAs(III)) and dimethylarsenite (DMAs(III)). Environmental arsenic is sensed by members of the ArsR/SmtB family. The arsR gene is autoregulated and is typically part of an operon that contains other ars genes involved in arsenic detoxification. To date every identified ArsR is regulated by inorganic As(III). Here we described a novel ArsR from Shewanella putrefaciens selective for MAs(III). SpArsR orthologs control expression of two MAs(III) resistance genes, arsP that encodes the ArsP MAs(III) efflux permease, and arsH encoding the ArsH MAs(III) oxidase. SpArsR has two conserved cysteine residues, Cys101 and Cys102. Mutation of either resulted in loss of MAs(III) binding, indicating that they form an MAs(III) binding site. SpArsR can be converted into an As(III)-responsive repressor by introduction of an additional cysteine that allows for three-coordinate As(III) binding. Our results indicate that SpArsR evolved selectivity for MAs(III) over As(III) in order to control expression of genes for MAs(III) detoxification.
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Affiliation(s)
- Jian Chen
- Department of Cellular Biology and Pharmacology, Herbert Wertheim College of Medicine, Florida International University, Miami, FL 33199, USA
| | - Venkadesh Sarkarai Nadar
- Department of Cellular Biology and Pharmacology, Herbert Wertheim College of Medicine, Florida International University, Miami, FL 33199, USA
| | - Barry P Rosen
- Department of Cellular Biology and Pharmacology, Herbert Wertheim College of Medicine, Florida International University, Miami, FL 33199, USA
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107
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Xue XM, Yan Y, Xiong C, Raber G, Francesconi K, Pan T, Ye J, Zhu YG. Arsenic biotransformation by a cyanobacterium Nostoc sp. PCC 7120. ENVIRONMENTAL POLLUTION (BARKING, ESSEX : 1987) 2017; 228:111-117. [PMID: 28527322 DOI: 10.1016/j.envpol.2017.05.005] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/09/2017] [Revised: 04/28/2017] [Accepted: 05/02/2017] [Indexed: 06/07/2023]
Abstract
Nostoc sp. PCC 7120 (Nostoc), a typical filamentous cyanobacterium ubiquitous in aquatic system, is recognized as a model organism to study prokaryotic cell differentiation and nitrogen fixation. In this study, Nostoc cells incubated with arsenite (As(III)) for two weeks were extracted with dichloromethane/methanol (DCM/MeOH) and the extract was partitioned between water and DCM. Arsenic species in aqueous and DCM layers were determined using high performance liquid chromatography - inductively coupled plasma mass spectrometer/electrospray tandem mass spectrometry (HPLC-ICPMS/ESIMSMS). In addition to inorganic arsenic (iAs), the aqueous layer also contained monomethylarsonate (MAs(V)), dimethylarsinate (DMAs(V)), and the two arsenosugars, namely a glycerol arsenosugar (Oxo-Gly) and a phosphate arsenosugar (Oxo-PO4). Two major arsenosugar phospholipids (AsSugPL982 and AsSugPL984) were detected in DCM fraction. Arsenic in the growth medium was also investigated by HPLC/ICPMS and shown to be present mainly as the inorganic forms As(III) and As(V) accounting for 29%-38% and 29%-57% of the total arsenic respectively. The total arsenic of methylated arsenic, arsenosugars, and arsenosugar phospholipids in Nostoc cells with increasing As(III) exposure were not markedly different, indicating that the transformation to organoarsenic in Nostoc was not dependent on As(III) concentration in the medium. Our results provide new insights into the role of cyanobacteria in the biogeochemical cycling of arsenic.
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Affiliation(s)
- Xi-Mei Xue
- Key Laboratory of Urban Environment and Health, Institute of Urban Environment, Chinese Academy of Sciences, Xiamen 361021, China
| | - Yu Yan
- Key Laboratory of Urban Environment and Health, Institute of Urban Environment, Chinese Academy of Sciences, Xiamen 361021, China; University of Chinese Academy of Sciences, Beijing 100049, China
| | - Chan Xiong
- Institute of Chemistry, University of Graz, Graz, 8010, Austria
| | - Georg Raber
- Institute of Chemistry, University of Graz, Graz, 8010, Austria
| | | | - Ting Pan
- Key Laboratory of Urban Environment and Health, Institute of Urban Environment, Chinese Academy of Sciences, Xiamen 361021, China; University of Chinese Academy of Sciences, Beijing 100049, China
| | - Jun Ye
- Key Laboratory of Urban Environment and Health, Institute of Urban Environment, Chinese Academy of Sciences, Xiamen 361021, China
| | - Yong-Guan Zhu
- Key Laboratory of Urban Environment and Health, Institute of Urban Environment, Chinese Academy of Sciences, Xiamen 361021, China; State Key Laboratory of Urban and Regional Ecology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China.
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108
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Recurrent horizontal transfer of arsenite methyltransferase genes facilitated adaptation of life to arsenic. Sci Rep 2017; 7:7741. [PMID: 28798375 PMCID: PMC5552862 DOI: 10.1038/s41598-017-08313-2] [Citation(s) in RCA: 51] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2017] [Accepted: 07/07/2017] [Indexed: 12/12/2022] Open
Abstract
The toxic metalloid arsenic has been environmentally ubiquitous since life first arose nearly four billion years ago and presents a challenge for the survival of all living organisms. Its bioavailability has varied dramatically over the history of life on Earth. As life spread, biogeochemical and climate changes cyclically increased and decreased bioavailable arsenic. To elucidate the history of arsenic adaptation across the tree of life, we reconstructed the phylogeny of the arsM gene that encodes the As(III) S-adenosylmethionine (SAM) methyltransferase. Our results suggest that life successfully moved into arsenic-rich environments in the late Archean Eon and Proterozoic Eon, respectively, by the spread of arsM genes. The arsM genes of bacterial origin have been transferred to other kingdoms of life on at least six occasions, and the resulting domesticated arsM genes promoted adaptation to environmental arsenic. These results allow us to peer into the history of arsenic adaptation of life on our planet and imply that dissemination of genes encoding diverse adaptive functions to toxic chemicals permit adaptation to changes in concentrations of environmental toxins over evolutionary history.
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109
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Zhu YG, Xue XM, Kappler A, Rosen BP, Meharg AA. Linking Genes to Microbial Biogeochemical Cycling: Lessons from Arsenic. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2017; 51:7326-7339. [PMID: 28602082 PMCID: PMC5871744 DOI: 10.1021/acs.est.7b00689] [Citation(s) in RCA: 163] [Impact Index Per Article: 23.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
Abstract
The biotransformation of arsenic is highly relevant to the arsenic biogeochemical cycle. Identification of the molecular details of microbial pathways of arsenic biotransformation coupled with analyses of microbial communities by meta-omics can provide insights into detailed aspects of the complexities of this biocycle. Arsenic transformations couple to other biogeochemical cycles, and to the fate of both nutrients and other toxic environmental contaminants. Microbial redox metabolism of iron, carbon, sulfur, and nitrogen affects the redox and bioavailability of arsenic species. In this critical review we illustrate the biogeochemical processes and genes involved in arsenic biotransformations. We discuss how current and future metagenomic-, metatranscriptomic-, metaproteomic-, and metabolomic-based methods will help to decipher individual microbial arsenic transformation processes, and their connections to other biogeochemical cycle. These insights will allow future use of microbial metabolic capabilities for new biotechnological solutions to environmental problems. To understand the complex nature of inorganic and organic arsenic species and the fate of environmental arsenic will require integrating systematic approaches with biogeochemical modeling. Finally, from the lessons learned from these studies of arsenic biogeochemistry, we will be able to predict how the environment changes arsenic, and, in response, how arsenic biotransformations change the environment.
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Affiliation(s)
- Yong-Guan Zhu
- Key Laboratory of Urban Environment and Health, Institute of Urban Environment, Chinese Academy of Sciences, Xiamen 361021, China
- State Key Laboratory of Urban and Regional Ecology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China
| | - Xi-Mei Xue
- Key Laboratory of Urban Environment and Health, Institute of Urban Environment, Chinese Academy of Sciences, Xiamen 361021, China
| | - Andreas Kappler
- Geomicrobiology, Center for Applied Geosciences, University of Tübingen, Tübingen 72076, Germany
| | - Barry P Rosen
- Department of Cellular Biology and Pharmacology, Herbert Wertheim College of Medicine, Florida International University, Miami, Florida 33199, United States
| | - Andrew A Meharg
- Institute for Global Food Security, Queen’s University Belfast, Belfast BT9 5HN, United Kingdom
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110
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Yan Y, Xue XM, Guo YQ, Zhu YG, Ye J. Co-expression of Cyanobacterial Genes for Arsenic Methylation and Demethylation in Escherichia coli Offers Insights into Arsenic Resistance. Front Microbiol 2017; 8:60. [PMID: 28174568 PMCID: PMC5258700 DOI: 10.3389/fmicb.2017.00060] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2016] [Accepted: 01/10/2017] [Indexed: 11/15/2022] Open
Abstract
Arsenite [As(III)] and methylarsenite [MAs(III)] are the most toxic inorganic and methylated arsenicals, respectively. As(III) and MAs(III) can be interconverted in the unicellular cyanobacterium Nostoc sp. PCC 7120 (Nostoc), which has both the arsM gene (NsarsM), which is responsible for arsenic methylation, and the arsI gene (NsarsI), which is responsible for MAs(III) demethylation. It is not clear how the cells prevent a futile cycle of methylation and demethylation. To investigate the relationship between arsenic methylation and demethylation, we constructed strains of Escherichia coli AW3110 (ΔarsRBC) expressing NsarsM or/and NsarsI. Expression of NsarsI conferred MAs(III) resistance through MAs(III) demethylation. Compared to NsArsI, NsArsM conferred higher resistance to As(III) and lower resistance to MAs(III) by methylating both As(III) and MAs(III). The major species found in solution was dimethylarsenate [DMAs(V)]. Co-expression of NsarsM and NsarsI conferred As(III) resistance at levels similar to that with NsarsM alone, although the main species found in solution after As(III) biotransformation was methylarsenate [MAs(V)] rather than DMAs(V). Co-expression of NsarsM and NsarsI conferred a higher level of resistance to MAs(III) than found with expression of NsarsM alone but lower than expression of only NsarsI. Cells co-expressing both genes converted MAs(III) to a mixture of As(III) and DMAs(V). In Nostoc NsarsM is constitutively expressed, while NsarsI is inducible by either As(III) or MAs(III). Thus, our results suggest that at low concentrations of arsenic, NsArsM activity predominates, while NsArsI activity predominates at high concentrations. We propose that coexistence of arsM and arsI genes in Nostoc could be advantageous for several reasons. First, it confers a broader spectrum of resistance to both As(III) and MAs(III). Second, at low concentrations of arsenic, the MAs(III) produced by NsArsM will possibly have antibiotic-like properties and give the organism a competitive advantage. Finally, these results shed light on the role of cyanobacteria in the arsenic biogeochemical cycle.
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Affiliation(s)
- Yu Yan
- Key Lab of Urban Environment and Health, Institute of Urban Environment – Chinese Academy of SciencesXiamen, China
- University of Chinese Academy of SciencesBeijing, China
| | - Xi-Mei Xue
- Key Lab of Urban Environment and Health, Institute of Urban Environment – Chinese Academy of SciencesXiamen, China
| | - Yu-Qing Guo
- Key Lab of Urban Environment and Health, Institute of Urban Environment – Chinese Academy of SciencesXiamen, China
- Fujian Provincial Key Laboratory of Agroecological Processing and Safety Monitoring, College of Life Sciences, Fujian Agriculture and Forestry UniversityFuzhou, China
| | - Yong-Guan Zhu
- Key Lab of Urban Environment and Health, Institute of Urban Environment – Chinese Academy of SciencesXiamen, China
- State Key Lab of Urban and Regional Ecology, Research Center for Eco-environmental Sciences – Chinese Academy of SciencesBeijing, China
| | - Jun Ye
- Key Lab of Urban Environment and Health, Institute of Urban Environment – Chinese Academy of SciencesXiamen, China
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111
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Chong TM, Yin WF, Chen JW, Mondy S, Grandclément C, Faure D, Dessaux Y, Chan KG. Comprehensive genomic and phenotypic metal resistance profile of Pseudomonas putida strain S13.1.2 isolated from a vineyard soil. AMB Express 2016; 6:95. [PMID: 27730570 PMCID: PMC5059233 DOI: 10.1186/s13568-016-0269-x] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2016] [Accepted: 10/04/2016] [Indexed: 11/17/2022] Open
Abstract
Trace metals are required in many cellular processes in bacteria but also induce toxic effects to cells when present in excess. As such, various forms of adaptive responses towards extracellular trace metal ions are essential for the survival and fitness of bacteria in their environment. A soil Pseudomonas putida, strain S13.1.2 has been isolated from French vineyard soil samples, and shown to confer resistance to copper ions. Further investigation revealed a high capacity to tolerate elevated concentrations of various heavy metals including nickel, cobalt, cadmium, zinc and arsenic. The complete genome analysis was conducted using single-molecule real-time (SMRT) sequencing and the genome consisted in a single chromosome at the size of 6.6 Mb. Presence of operons and gene clusters such as cop, cus, czc, nik, and asc systems were detected and accounted for the observed resistance phenotypes. The unique features in terms of specificity and arrangements of some genetic determinants were also highlighted in the study. Our findings has provided insights into the adaptation of this strain to accumulation and persistence of copper and other heavy metals in vineyard soil environment.
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112
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Resistance of Permafrost and Modern Acinetobacter lwoffii Strains to Heavy Metals and Arsenic Revealed by Genome Analysis. BIOMED RESEARCH INTERNATIONAL 2016; 2016:3970831. [PMID: 27795957 PMCID: PMC5067307 DOI: 10.1155/2016/3970831] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/20/2016] [Revised: 07/14/2016] [Accepted: 09/07/2016] [Indexed: 12/23/2022]
Abstract
We performed whole-genome sequencing of five permafrost strains of Acinetobacter lwoffii (frozen for 15–3000 thousand years) and analyzed their resistance genes found in plasmids and chromosomes. Four strains contained multiple plasmids (8–12), which varied significantly in size (from 4,135 to 287,630 bp) and genetic structure; the fifth strain contained only two plasmids. All large plasmids and some medium-size and small plasmids contained genes encoding resistance to various heavy metals, including mercury, cobalt, zinc, cadmium, copper, chromium, and arsenic compounds. Most resistance genes found in the ancient strains of A. lwoffii had their closely related counterparts in modern clinical A. lwoffii strains that were also located on plasmids. The vast majority of the chromosomal resistance determinants did not possess complete sets of the resistance genes or contained truncated genes. Comparative analysis of various A. lwoffii and of A. baumannii strains discovered a number of differences between them: (i) chromosome sizes in A. baumannii exceeded those in A. lwoffii by about 20%; (ii) on the contrary, the number of plasmids in A. lwoffii and their total size were much higher than those in A. baumannii; (iii) heavy metal resistance genes in the environmental A. lwoffii strains surpassed those in A. baumannii strains in the number and diversity and were predominantly located on plasmids. Possible reasons for these differences are discussed.
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113
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Chen J, Rosen BP. Organoarsenical Biotransformations by Shewanella putrefaciens. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2016; 50:7956-63. [PMID: 27366920 PMCID: PMC4984541 DOI: 10.1021/acs.est.6b00235] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/13/2023]
Abstract
Microbes play a critical role in the global arsenic biogeocycle. Most studies have focused on redox cycling of inorganic arsenic in bacteria and archaea. The parallel cycles of organoarsenical biotransformations are less well characterized. Here we describe organoarsenical biotransformations in the environmental microbe Shewanella putrefaciens. Under aerobic growth conditions, S. putrefaciens reduced the herbicide MSMA (methylarsenate or MAs(V)) to methylarsenite (MAs(III)). Even though it does not contain an arsI gene, which encodes the ArsI C-As lyase, S. putrefaciens demethylated MAs(III) to As(III). It cleaved the C-As bond in aromatic arsenicals such as the trivalent forms of the antimicrobial agents roxarsone (Rox(III)), nitarsone (Nit(III)) and phenylarsenite (PhAs(III)), which have been used as growth promoters for poultry and swine. S. putrefaciens thiolated methylated arsenicals, converting MAs(V) into the more toxic metabolite monomethyl monothioarsenate (MMMTAs(V)), and transformed dimethylarsenate (DMAs(V)) into dimethylmonothioarsenate (DMMTAs(V)). It also reduced the nitro groups of Nit(V), forming p-aminophenyl arsenate (p-arsanilic acid or p-AsA(V)), and Rox(III), forming 3-amino-4-hydroxybenzylarsonate (3A4HBzAs(V)). Elucidation of organoarsenical biotransformations by S. putrefaciens provides a holistic appreciation of how these environmental pollutants are degraded.
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Affiliation(s)
| | - Barry P. Rosen
- Corresponding Author. Phone: (+1) 305-348-0657; fax: (+1) 305-348-0651;
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114
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Paralogous Regulators ArsR1 and ArsR2 of Pseudomonas putida KT2440 as a Basis for Arsenic Biosensor Development. Appl Environ Microbiol 2016; 82:4133-4144. [PMID: 27208139 DOI: 10.1128/aem.00606-16] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2016] [Accepted: 04/25/2016] [Indexed: 11/20/2022] Open
Abstract
UNLABELLED The remarkable metal resistance of many microorganisms is related to the presence of multiple metal resistance operons. Pseudomonas putida KT2440 can be considered a model for these microorganisms since its arsenic resistance is due to the action of proteins encoded by the two paralogous arsenic resistance operons ARS1 and ARS2. Both operons contain the genes encoding the transcriptional regulators ArsR1 and ArsR2 that control operon expression. We show here that purified ArsR1 and ArsR2 bind the trivalent salt of arsenic (arsenite) with similar affinities (~30 μM), whereas no binding is observed for the pentavalent salt (arsenate). Furthermore, trivalent salts of bismuth and antimony showed binding to both paralogues. The positions of cysteines, found to bind arsenic in other homologues, indicate that ArsR1 and ArsR2 employ different modes of arsenite recognition. Both paralogues are dimeric and possess significant thermal stability. Both proteins were used to construct whole-cell, lacZ-based biosensors. Whereas responses to bismuth were negligible, significant responses were observed for arsenite, arsenate, and antimony. Biosensors based on the P. putida arsB1 arsB2 arsenic efflux pump double mutant were significantly more sensitive than biosensors based on the wild-type strain. This sensitivity enhancement by pump mutation may be a convenient strategy for the construction of other biosensors. A frequent limitation found for other arsenic biosensors was their elevated background signal and interference by inorganic phosphate. The constructed biosensors show no interference by inorganic phosphate, are characterized by a very low background signal, and were found to be suitable to analyze environmental samples. IMPORTANCE Arsenic is at the top of the priority list of hazardous compounds issued by the U.S. Agency for Toxic Substances and Disease. The reason for the stunning arsenic resistance of many microorganisms is the existence of paralogous arsenic resistance operons. Pseudomonas putida KT2440 is a model organism for such bacteria, and their duplicated ars operons and in particular their ArsR transcription regulators have been studied in depth by in vivo approaches. Here we present an analysis of both purified ArsR paralogues by different biophysical techniques, and data obtained provide valuable insight into their structure and function. Particularly insightful was the comparison of ArsR effector profiles determined by in vitro and in vivo experimentation. We also report the use of both paralogues to construct robust and highly sensitive arsenic biosensors. Our finding that the deletion of both arsenic efflux pumps significantly increases biosensor sensitivity is of general relevance in the biosensor field.
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Li J, Mandal G, Rosen BP. Expression of arsenic resistance genes in the obligate anaerobe Bacteroides vulgatus ATCC 8482, a gut microbiome bacterium. Anaerobe 2016; 39:117-23. [PMID: 27040269 PMCID: PMC4984537 DOI: 10.1016/j.anaerobe.2016.03.012] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2016] [Revised: 03/27/2016] [Accepted: 03/28/2016] [Indexed: 11/26/2022]
Abstract
The response of the obligate anaerobe Bacteroides vulgatus ATCC 8482, a common human gut microbiota, to arsenic was determined. B. vulgatus ATCC 8482 is highly resistant to pentavalent As(V) and methylarsenate (MAs(V)). It is somewhat more sensitive to trivalent inorganic As(III) but 100-fold more sensitive to methylarsenite (MAs(III)) than to As(III). B. vulgatus ATCC 8482 has eight continuous genes in its genome that we demonstrate form an arsenical-inducible transcriptional unit. The first gene of this ars operon, arsR, encodes a putative ArsR As(III)-responsive transcriptional repressor. The next three genes encode proteins of unknown function. The remaining genes, arsDABC, have well-characterized roles in detoxification of inorganic arsenic, but there are no known genes for MAs(III) resistance. Expression of each gene after exposure to trivalent and pentavalent inorganic and methylarsenicals was analyzed. MAs(III) was the most effective inducer. The arsD gene was the most highly expressed of the ars operon genes. These results demonstrate that this anaerobic microbiome bacterium has arsenic-responsive genes that confer resistance to inorganic arsenic and may be responsible for the organism's ability to maintain its prevalence in the gut following dietary exposure to inorganic arsenic.
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Affiliation(s)
- Jiaojiao Li
- Department of Cellular Biology and Pharmacology, Herbert Wertheim College of Medicine, Florida International University, Miami, FL, 33199, United States
| | - Goutam Mandal
- Department of Cellular Biology and Pharmacology, Herbert Wertheim College of Medicine, Florida International University, Miami, FL, 33199, United States
| | - Barry P Rosen
- Department of Cellular Biology and Pharmacology, Herbert Wertheim College of Medicine, Florida International University, Miami, FL, 33199, United States.
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Regulatory Activities of Four ArsR Proteins in Agrobacterium tumefaciens 5A. Appl Environ Microbiol 2016; 82:3471-3480. [PMID: 27037117 DOI: 10.1128/aem.00262-16] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2016] [Accepted: 03/28/2016] [Indexed: 02/08/2023] Open
Abstract
UNLABELLED 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. IMPORTANCE Given 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.
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Chen J, Yoshinaga M, Garbinski LD, Rosen BP. Synergistic interaction of glyceraldehydes-3-phosphate dehydrogenase and ArsJ, a novel organoarsenical efflux permease, confers arsenate resistance. Mol Microbiol 2016; 100:945-53. [PMID: 26991003 DOI: 10.1111/mmi.13371] [Citation(s) in RCA: 54] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/12/2016] [Indexed: 11/28/2022]
Abstract
Microbial biotransformations are major contributors to the arsenic biogeocycle. In parallel with transformations of inorganic arsenic, organoarsenicals pathways have recently been recognized as important components of global cycling of arsenic. The well-characterized pathway of resistance to arsenate is reduction coupled to arsenite efflux. Here, we describe a new pathway of arsenate resistance involving biosynthesis and extrusion of an unusual pentavalent organoarsenical. A number of arsenic resistance (ars) operons have two genes of unknown function that are linked in these operons. One, gapdh, encodes the glycolytic enzyme glyceraldehyde-3-phosphate dehydrogenase. The other, arsJ, encodes a major facilitator superfamily (MFS) protein. The two genes were cloned from the chromosome of Pseudomonas aeruginosa. When expressed together, but not alone, in Escherichia coli, gapdh and arsJ specifically conferred resistance to arsenate and decreased accumulation of As(V). Everted membrane vesicles from cells expressing arsJ accumulated As(V) in the presence of purified GAPDH, D-glceraldehylde 3-phosphate (G3P) and NAD(+) . GAPDH forms the unstable organoarsenical 1-arseno-3-phosphoglycerate (1As3PGA). We propose that ArsJ is an efflux permease that extrudes 1As3PGA from cells, where it rapidly dissociates into As(V) and 3-phosphoglycerate (3PGA), creating a novel pathway of arsenate resistance.
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Affiliation(s)
- Jian Chen
- Department of Cellular Biology and Pharmacology, Herbert Wertheim College of Medicine, Florida International University, Miami, FL, 33199, USA
| | - Masafumi Yoshinaga
- Department of Cellular Biology and Pharmacology, Herbert Wertheim College of Medicine, Florida International University, Miami, FL, 33199, USA
| | - Luis D Garbinski
- Department of Cellular Biology and Pharmacology, Herbert Wertheim College of Medicine, Florida International University, Miami, FL, 33199, USA
| | - Barry P Rosen
- Department of Cellular Biology and Pharmacology, Herbert Wertheim College of Medicine, Florida International University, Miami, FL, 33199, USA
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Gillan DC. Metal resistance systems in cultivated bacteria: are they found in complex communities? Curr Opin Biotechnol 2016; 38:123-30. [DOI: 10.1016/j.copbio.2016.01.012] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2015] [Revised: 01/27/2016] [Accepted: 01/28/2016] [Indexed: 12/11/2022]
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Abstract
Arsenic is the most pervasive environmental substance and is classified by the International Agency for Research on Cancer as a Group 1 human carcinogen. Nearly every organism has resistance pathways for inorganic arsenic, and in bacteria, their genes are found in arsenic resistance (ars) operons. Recently, a parallel pathway for organic arsenicals has been identified. The ars genes responsible for the organoarsenical detoxification includes arsM, which encodes an As(III) S-adenosylmethionine methyltransferase, arsI, which encodes a C–As bond lyase, and arsH, which encodes a methylarsenite oxidase. The identification and properties of arsM, arsI and arsH are described in this review.
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Andres J, Bertin PN. The microbial genomics of arsenic. FEMS Microbiol Rev 2016; 40:299-322. [DOI: 10.1093/femsre/fuv050] [Citation(s) in RCA: 130] [Impact Index Per Article: 16.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 12/28/2015] [Indexed: 12/17/2022] Open
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Yan Y, Ye J, Xue XM, Zhu YG. Arsenic Demethylation by a C·As Lyase in Cyanobacterium Nostoc sp. PCC 7120. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2015; 49:14350-14358. [PMID: 26544154 DOI: 10.1021/acs.est.5b03357] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
Arsenic, a ubiquitous toxic substance, exists mainly as inorganic forms in the environment. It is perceived that organoarsenicals can be demethylated and degraded into inorganic arsenic by microorganisms. Few studies have focused on the mechanism of arsenic demethylation in bacteria. Here, we investigated arsenic demethylation in a typical freshwater cyanobacterium Nostoc sp. PCC 7120. This bacterium was able to demethylate monomethylarsenite [MAs(III)] rapidly to arsenite [As(III)] and also had the ability to demethylate monomethylarsenate [MAs(V)] to As(III). The NsarsI encoding a C·As lyase responsible for MAs(III) demethylation was cloned from Nostoc sp. PCC 7120 and heterologously expressed in an As-hypersensitive strain Escherichia coli AW3110 (ΔarsRBC). Expression of NsarsI was shown to confer MAs(III) resistance through arsenic demethylation. The purified NsArsI was further identified and functionally characterized in vitro. NsArsI existed mainly as the trimeric state, and the kinetic data were well-fit to the Hill equation with K0.5 = 7.55 ± 0.33 μM for MAs(III), Vmax = 0.79 ± 0.02 μM min(-1), and h = 2.7. Both of the NsArsI truncated derivatives lacking the C-terminal 10 residues (ArsI10) or 23 residues (ArsI23) had a reduced ability of MAs(III) demethylation. These results provide new insights for understanding the important role of cyanobacteria in arsenic biogeochemical cycling in the environment.
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Affiliation(s)
- Yu Yan
- Key Lab of Urban Environment and Health, Institute of Urban Environment, Chinese Academy of Sciences , Xiamen 361021, People's Republic of China
- University of Chinese Academy of Sciences , Beijing 100049, People's Republic of China
| | - Jun Ye
- Key Lab of Urban Environment and Health, Institute of Urban Environment, Chinese Academy of Sciences , Xiamen 361021, People's Republic of China
| | - Xi-Mei Xue
- Key Lab of Urban Environment and Health, Institute of Urban Environment, Chinese Academy of Sciences , Xiamen 361021, People's Republic of China
| | - Yong-Guan Zhu
- Key Lab of Urban Environment and Health, Institute of Urban Environment, Chinese Academy of Sciences , Xiamen 361021, People's Republic of China
- State Key Lab of Urban and Regional Ecology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences , Beijing 100085, People's Republic of China
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Chen J, Madegowda M, Bhattacharjee H, Rosen BP. ArsP: a methylarsenite efflux permease. Mol Microbiol 2015; 98:625-35. [PMID: 26234817 DOI: 10.1111/mmi.13145] [Citation(s) in RCA: 70] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/23/2015] [Indexed: 01/22/2023]
Abstract
Trivalent organoarsenic compounds are far more toxic than either pentavalent organoarsenicals or inorganic arsenite. Many microbes methylate inorganic arsenite (As(III)) to more toxic and carcinogenic methylarsenite (MAs(III)). Additionally, monosodium methylarsenate (MSMA or MAs(V)) has been used widely as an herbicide and is reduced by microbial communities to MAs(III). Roxarsone (3-nitro-4-hydroxybenzenearsonic acid) is a pentavalent aromatic arsenical that is used as antimicrobial growth promoter for poultry and swine, and its active form is the trivalent species Rox(III). A bacterial permease, ArsP, from Campylobacter jejuni, was recently shown to confer resistance to roxarsone. In this study, C. jejuni arsP was expressed in Escherichia coli and shown to confer resistance to MAs(III) and Rox(III) but not to inorganic As(III) or pentavalent organoarsenicals. Cells of E. coli expressing arsP did not accumulate trivalent organoarsenicals. Everted membrane vesicles from those cells accumulated MAs(III) > Rox(III) with energy supplied by NADH oxidation, reflecting efflux from cells. The vesicles did not transport As(III), MAs(V) or pentavalent roxarsone. Mutation or modification of the two conserved cysteine residues resulted in loss of transport activity, suggesting that they play a role in ArsP function. Thus, ArsP is the first identified efflux system specific for trivalent organoarsenicals.
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Affiliation(s)
- Jian Chen
- Department of Cellular Biology and Pharmacology, Herbert Wertheim College of Medicine, Florida International University, Miami, FL, 33199, USA
| | - Mahendra Madegowda
- Department of Cellular Biology and Pharmacology, Herbert Wertheim College of Medicine, Florida International University, Miami, FL, 33199, USA
| | - Hiranmoy Bhattacharjee
- Department of Cellular Biology and Pharmacology, Herbert Wertheim College of Medicine, Florida International University, Miami, FL, 33199, USA
| | - Barry P Rosen
- Department of Cellular Biology and Pharmacology, Herbert Wertheim College of Medicine, Florida International University, Miami, FL, 33199, USA
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Draft Genome Sequence of Burkholderia sp. MR1, a Methylarsenate-Reducing Bacterial Isolate from Florida Golf Course Soil. GENOME ANNOUNCEMENTS 2015; 3:3/3/e00608-15. [PMID: 26044439 PMCID: PMC4457076 DOI: 10.1128/genomea.00608-15] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
To elucidate the environmental organoarsenical biocycle, we isolated a soil organism, Burkholderia sp. MR1, which reduces relatively nontoxic pentavalent methylarsenate to the more toxic trivalent methylarsenite, with the goal of identifying the gene for the reductase. Here, we report the draft genome sequence of Burkholderia sp. MR1.
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