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1.
Ecotoxicol Environ Saf ; 221: 112415, 2021 Sep 15.
Artigo em Inglês | MEDLINE | ID: mdl-34171691

RESUMO

In order to understand the mechanisms of arsenic (As) accumulation and detoxification in aquatic plants exposed to different As species, a hydroponic experiment was conducted and the three aquatic plants (Hydrilla verticillata, Pistia stratiotes and Eichhornia crassipes) were exposed to different concentrations of As(III), As(V) and dimethylarsinate (DMA) for 10 days. The biomass, the surface As adsorption and total As adsorption of three plants were determined. Furthermore, As speciation in the culture solution and plant body, as well as the arsenate reductase (AR) activities of roots and shoots, were also analyzed. The results showed that the surface As adsorption of plants was far less than total As absorption. Compared to As(V), the plants showed a lower DMA accumulation. P. stratiotes showed the highest accumulation of inorganic arsenic but E. crassipes showed the lowest at the same As treatment. E. crassipes showed a strong ability to accumulate DMA. Results from As speciation analysis in culture solution showed that As(III) was transformed to As(V) in all As(III) treatments, and the oxidation rates followed as the sequence of H. verticillata>P. stratiotes>E. crassipes>no plant. As(III) was the predominant species in both roots (39.4-88.3%) and shoots (39-86%) of As(III)-exposed plants. As(V) and As(III) were the predominant species in roots (37-94%) and shoots (31.1-85.6%) in As(V)-exposed plants, respectively. DMA was the predominant species in both roots (23.46-100%) and shoots (72.6-100%) in DMA-exposed plants. The As(III) contents and AR activities in the roots of P. stratiotes and in the shoots of H. verticillata were significantly increased when exposed to 1 mg·L-1 or 3 mg·L-1 As(V). Therefore, As accumulation mainly occurred via biological uptake rather than physicochemical adsorption, and AR played an important role in As detoxification in aquatic plants. In the case of As(V)-exposed plants, their As tolerance was attributed to the increase of AR activities.


Assuntos
Araceae , Arseniato Redutases/metabolismo , Arsênio , Ácido Cacodílico , Eichhornia , Hydrocharitaceae , Proteínas de Plantas/metabolismo , Poluentes Químicos da Água , Adsorção , Araceae/química , Araceae/metabolismo , Arsênio/química , Arsênio/metabolismo , Ácido Cacodílico/química , Ácido Cacodílico/metabolismo , Eichhornia/química , Eichhornia/metabolismo , Hydrocharitaceae/química , Hydrocharitaceae/metabolismo , Hidroponia , Raízes de Plantas/química , Raízes de Plantas/metabolismo , Brotos de Planta/química , Brotos de Planta/metabolismo , Poluentes Químicos da Água/química , Poluentes Químicos da Água/metabolismo
2.
Sci Rep ; 11(1): 6794, 2021 03 24.
Artigo em Inglês | MEDLINE | ID: mdl-33762609

RESUMO

This study evaluated the phytoextraction capacity of the fern Pteris vittata grown on a natural arsenic-rich soil of volcanic-origin from the Viterbo area in central Italy. This calcareous soil is characterized by an average arsenic concentration of 750 mg kg-1, of which 28% is bioavailable. By means of micro-energy dispersive X-ray fluorescence spectrometry (µ-XRF) we detected As in P. vittata fronds after just 10 days of growth, while a high As concentrations in fronds (5,000 mg kg-1), determined by Inductively coupled plasma-optical emission spectrometry (ICP-OES), was reached after 5.5 months. Sixteen arsenate-tolerant bacterial strains were isolated from the P. vittata rhizosphere, a majority of which belong to the Bacillus genus, and of this majority only two have been previously associated with As. Six bacterial isolates were highly As-resistant (> 100 mM) two of which, homologous to Paenarthrobacter ureafaciens and Beijerinckia fluminensis, produced a high amount of IAA and siderophores and have never been isolated from P. vittata roots. Furthermore, five isolates contained the arsenate reductase gene (arsC). We conclude that P. vittata can efficiently phytoextract As when grown on this natural As-rich soil and a consortium of bacteria, largely different from that usually found in As-polluted soils, has been found in P. vittata rhizosphere.


Assuntos
Arsênio/análise , Beijerinckiaceae/metabolismo , Micrococcaceae/metabolismo , Pteris/química , Solo/química , Arseniato Redutases/genética , Arseniato Redutases/metabolismo , Arsênio/metabolismo , Arsênio/toxicidade , Proteínas de Bactérias/genética , Proteínas de Bactérias/metabolismo , Beijerinckiaceae/química , Beijerinckiaceae/isolamento & purificação , Biodegradação Ambiental , Farmacorresistência Bacteriana/genética , Micrococcaceae/química , Micrococcaceae/isolamento & purificação , Raízes de Plantas/química , Raízes de Plantas/metabolismo , Raízes de Plantas/microbiologia , Pteris/metabolismo , Pteris/microbiologia , Rizosfera , Sideróforos/análise , Sideróforos/metabolismo , Microbiologia do Solo , Poluentes do Solo/análise , Poluentes do Solo/metabolismo , Espectrofotometria Atômica
3.
Biochemistry ; 60(6): 465-476, 2021 02 16.
Artigo em Inglês | MEDLINE | ID: mdl-33538578

RESUMO

The anaerobic bacterium Chrysiogenes arsenatis respires using the oxyanion arsenate (AsO43-) as the terminal electron acceptor, where it is reduced to arsenite (AsO33-) while concomitantly oxidizing various organic (e.g., acetate) electron donors. This respiratory activity is catalyzed in the periplasm of the bacterium by the enzyme arsenate reductase (Arr), with expression of the enzyme controlled by a sensor histidine kinase (ArrS) and a periplasmic-binding protein (PBP), ArrX. Here, we report for the first time, the molecular structure of ArrX in the absence and presence of bound ligand arsenate. Comparison of the ligand-bound structure of ArrX with other PBPs shows a high level of conservation of critical residues for ligand binding by these proteins; however, this suite of PBPs shows different structural alterations upon ligand binding. For ArrX and its homologue AioX (from Rhizobium sp. str. NT-26), which specifically binds arsenite, the structures of the substrate-binding sites in the vicinity of a conserved and critical cysteine residue contribute to the discrimination of binding for these chemically similar ligands.


Assuntos
Arseniato Redutases/química , Bactérias/metabolismo , Sequência de Aminoácidos/genética , Arseniato Redutases/metabolismo , Arseniatos/química , Arseniatos/metabolismo , Bactérias/química , Composição de Bases/genética , Sítios de Ligação , Catálise , Cristalografia por Raios X/métodos , Histidina Quinase/metabolismo , Oxirredutases/metabolismo , Periplasma/metabolismo , Proteínas Periplásmicas de Ligação/química , Proteínas Periplásmicas de Ligação/metabolismo , Filogenia , RNA Ribossômico 16S/genética , Análise de Sequência de DNA/métodos
4.
Sci Rep ; 11(1): 2991, 2021 02 04.
Artigo em Inglês | MEDLINE | ID: mdl-33542380

RESUMO

The correct immobilization and orientation of enzymes on nanosurfaces is a crucial step either for the realization of biosensors, as well as to guarantee the efficacy of the developed biomaterials. In this work we produced two versions of a chimeric protein, namely ArsC-Vmh2 and Vmh2-ArsC, which combined the self-assembling properties of Vmh2, a hydrophobin from Pleurotus ostreatus, with that of TtArsC, a thermophilic arsenate reductase from Thermus thermophilus; both chimeras were heterologously expressed in Escherichia coli and purified from inclusion bodies. They were characterized for their enzymatic capability to reduce As(V) into As(III), as well as for their immobilization properties on polystyrene and gold in comparison to the native TtArsC. The chimeric proteins immobilized on polystyrene can be reused up to three times and stored for 15 days with 50% of activity loss. Immobilization on gold electrodes showed that both chimeras follow a classic Langmuir isotherm model towards As(III) recognition, with an association constant (KAsIII) between As(III) and the immobilized enzyme, equal to 650 (± 100) L mol-1 for ArsC-Vmh2 and to 1200 (± 300) L mol-1 for Vmh2-ArsC. The results demonstrate that gold-immobilized ArsC-Vmh2 and Vmh2-ArsC can be exploited as electrochemical biosensors to detect As(III).


Assuntos
Arseniato Redutases/química , Arsênio/isolamento & purificação , Técnicas Biossensoriais , Proteínas Fúngicas/química , Proteínas Recombinantes de Fusão/química , Arsênio/toxicidade , Enzimas Imobilizadas/química , Escherichia coli/genética , Humanos , Pleurotus/química , Pleurotus/enzimologia , Thermus thermophilus/enzimologia
5.
J Exp Bot ; 72(2): 415-425, 2021 02 02.
Artigo em Inglês | MEDLINE | ID: mdl-33038235

RESUMO

High Arsenic Concentration 1 (HAC1), an Arabidopsis thaliana arsenate reductase, plays a key role in arsenate [As(V)] tolerance. Through conversion of As(V) to arsenite [As(III)], HAC1 enables As(III) export from roots, and restricts translocation of As(V) to shoots. To probe the ability of different root tissues to detoxify As(III) produced by HAC1, we generated A. thaliana lines expressing HAC1 in different cell types. We investigated the As(V) tolerance phenotypes: root growth, As(III) efflux, As translocation, and As chemical speciation. We showed that HAC1 can function in the outer tissues of the root (epidermis, cortex, and endodermis) to confer As(V) tolerance, As(III) efflux, and limit As accumulation in shoots. HAC1 is less effective in the stele at conferring As(V) tolerance phenotypes. The exception is HAC1 activity in the protoxylem, which we found to be sufficient to restrict As translocation, but not to confer As(V) tolerance. In conclusion, we describe cell type-specific functions of HAC1 that spatially separate the control of As(V) tolerance and As translocation. Further, we identify a key function of protoxylem cells in As(V) translocation, consistent with the model where endodermal passage cells, above protoxylem pericycle cells, form a 'funnel' loading nutrients and potentially toxic elements into the vasculature.


Assuntos
Proteínas de Arabidopsis , Arabidopsis , Arsênio , Arabidopsis/genética , Proteínas de Arabidopsis/genética , Arseniato Redutases , Arseniatos , Raízes de Plantas/genética , Brotos de Planta
6.
Appl Biochem Biotechnol ; 193(1): 1-18, 2021 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-32809107

RESUMO

The arsC gene-encoded arsenate reductase is a vital catalytic enzyme for remediation of environmental arsenic (As). Microorganisms containing the arsC gene can convert pentavalent arsenate (As[V]) to trivalent arsenite (As[III]) to be either retained in the bacterial cell or released into the air. The molecular mechanism governing this process is unknown. Here we present an in silico model of the enzyme to describe their probable active site cavities using SCFBio servers. We retrieved the amino acid sequence of bacterial arsenate reductase enzymes in FASTA format from the NCBI database. Enzyme structure was predicted using the I-TASSER server and visualized using PyMOL tools. The ProSA and the PROCHECK servers were used to evaluate the overall significance of the predicted model. Accordingly, arsenate reductase from Streptococcus pyogenes, Oligotropha carboxidovorans OM5, Rhodopirellula baltica SH 1, and Serratia ureilytica had the highest quality scores with statistical significance. The plausible cavities of the active site were identified in our examined arsenate reductase enzymes which were abundant in glutamate and lysine residues with 6 to 16 amino acids. This in silico experiment may contribute greatly to the remediation of arsenic pollution through the utilization of microbial species.


Assuntos
Arseniato Redutases/química , Bactérias/enzimologia , Proteínas de Bactérias/química , Simulação de Dinâmica Molecular , Sequência de Aminoácidos , Domínio Catalítico
7.
J Integr Plant Biol ; 63(4): 755-771, 2021 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-33325122

RESUMO

In eukaryotes, MEDIATOR is a conserved multi-subunit complex that links transcription factors and RNA polymerase II and that thereby facilitates transcriptional initiation. Although the composition of MEDIATOR has been well studied in yeast and mammals, relatively little is known about the composition of MEDIATOR in plants. By affinity purification followed by mass spectrometry, we identified 28 conserved MEDIATOR subunits in Arabidopsis thaliana, including putative MEDIATOR subunits that were not previously validated. Our results indicated that MED34, MED35, MED36, and MED37 are not Arabidopsis MEDIATOR subunits, as previously proposed. Our results also revealed that two homologous CBP/p300 histone acetyltransferases, HAC1 and HAC5 (HAC1/5) are in fact plant-specific MEDIATOR subunits. The MEDIATOR subunits MED8 and MED25 (MED8/25) are partially responsible for the association of MEDIATOR with HAC1/5, MED8/25 and HAC1/5 co-regulate gene expression and thereby affect flowering time and floral development. Our in vitro observations indicated that MED8 and HAC1 form liquid-like droplets by phase separation, and our in vivo observations indicated that these droplets co-localize in the nuclear bodies at a subset of nuclei. The formation of liquid-like droplets is required for MED8 to interact with RNA polymerase II. In summary, we have identified all of the components of Arabidopsis MEDIATOR and revealed the mechanism underlying the link of histone acetylation and transcriptional regulation.


Assuntos
Proteínas de Arabidopsis/metabolismo , Arabidopsis/metabolismo , Flores/metabolismo , Plantas Geneticamente Modificadas/metabolismo , Arabidopsis/genética , Proteínas de Arabidopsis/genética , Arseniato Redutases/genética , Arseniato Redutases/metabolismo , Flores/genética , Regulação da Expressão Gênica de Plantas , Histonas/genética , Histonas/metabolismo , Complexo Mediador/genética , Complexo Mediador/metabolismo , Plantas Geneticamente Modificadas/genética , RNA Polimerase II/genética , RNA Polimerase II/metabolismo
8.
Biochemistry ; 59(44): 4262-4284, 2020 11 10.
Artigo em Inglês | MEDLINE | ID: mdl-33135415

RESUMO

Arsenate reductase (ArsC) is a superfamily of enzymes that reduce arsenate. Due to active site similarities, some ArsC can function as low-molecular weight protein tyrosine phosphatases (LMW-PTPs). Broad superfamily classifications align with redox partners (Trx- or Grx-linked). To understand this superfamily's mechanistic diversity, the ArsC superfamily is classified on the basis of active site features utilizing the tools TuLIP (two-level iterative clustering process) and autoMISST (automated multilevel iterative sequence searching technique). This approach identified nine functionally relevant (perhaps isofunctional) protein groups. Five groups exhibit distinct ArsC mechanisms. Three are Grx-linked: group 4AA (classical ArsC), group 3AAA (YffB-like), and group 5BAA. Two are Trx-linked: groups 6AAAAA and 7AAAAAAAA. One is an Spx-like transcriptional regulatory group, group 5AAA. Three are potential LMW-PTP groups: groups 7BAAAA, and 7AAAABAA, which have not been previously identified, and the well-studied LMW-PTP family group 8AAA. Molecular dynamics simulations were utilized to explore functional site details. In several families, we confirm and add detail to literature-based mechanistic information. Mechanistic roles are hypothesized for conserved active site residues in several families. In three families, simulations of the unliganded structure sample specific conformational ensembles, which are proposed to represent either a more ligand-binding-competent conformation or a pathway toward a more binding-competent state; these active sites may be designed to traverse high-energy barriers to the lower-energy conformations necessary to more readily bind ligands. This more detailed biochemical understanding of ArsC and ArsC-like PTP mechanisms opens possibilities for further understanding of arsenate bioremediation and the LMW-PTP mechanism.


Assuntos
Arseniato Redutases/química , Biologia Computacional , Sequência de Aminoácidos , Domínio Catalítico , Simulação de Dinâmica Molecular , Alinhamento de Sequência
9.
Environ Sci Technol ; 54(21): 14107-14113, 2020 11 03.
Artigo em Inglês | MEDLINE | ID: mdl-33054201

RESUMO

Microbial antimonate [Sb(V)] respiratory reduction is an important process regulating Sb redox transformation in the environment. However, little is known about the microbial respiratory reductase for Sb(V). Herein, we report Sb(V)-respiring reduction by Shewanella sp. ANA-3 through an arsenate respiratory reductase encoded by arrAB. Incubation experiments showed that Shewanella sp. ANA-3 mediated Sb(V)-respiring reduction, which was dependent on the cell concentration. Both protein analysis and reverse transcriptase-polymerase chain reaction results revealed that arrAB was highly expressed in Sb(V)-respiring reduction. In vivo evidence with mutants indicated that neither ANA-3-ΔarrA nor ANA-3-ΔarrB was capable of reducing Sb(V) as efficiently as the wild type, whereas complementation by the wild-type sequences of arrA and arrB rescued the mutants' ability. Our in vitro results showed that ArrAB purified by His-Tag was able to mediate Sb(V) reduction, though with much suppressed catalytic kinetics compared with As(V) reduction. The cell-concentration-dependent reduction of Sb(V) was regulated by quorum sensing via the luxS gene. This study opens a new chapter in the mechanistic understanding of microbial Sb(V) respiratory reduction.


Assuntos
Shewanella , Arseniato Redutases , Proteínas de Bactérias/metabolismo , Oxirredução , Oxirredutases/metabolismo , Shewanella/genética , Shewanella/metabolismo
10.
J Hazard Mater ; 399: 122895, 2020 11 15.
Artigo em Inglês | MEDLINE | ID: mdl-32937698

RESUMO

Arsenic-hyperaccumulator Pteris vittata is efficient in As absorption, reduction, and translocation. But the molecular mechanisms and locations of arsenate (AsV) reduction in P. vittata are still unclear. Here, we identified two new arsenate reductase genes from P. vittata, PvHAC1 and PvHAC2. Two PvHAC genes encoded a rhodanase-like protein, which were localized in the cytoplasm and nucleus. Both recombinant Escherichia coli strains and transgenic Arabidopsis thaliana lines showed arsenate reductase ability after expressing PvHAC genes. Further, expressing PvHAC2 enhanced As tolerance and reduced As accumulation in A. thaliana shoots under AsV exposure. Based on expression pattern analysis, PvHAC1 and PvHAC2 were predominantly expressed in the rhizomes and fronds of P. vittata. Different from those of HAC homologous genes in non-hyperaccumulators, little PvHAC was expressed in the roots. Besides, PvHAC1 expression was strongly upregulated under AsV exposure but not AsIII. The data suggest that arsenate reductase PvHAC1 in the rhizomes coupled with arsenate reductase PvHAC2 in the fronds of P. vittata played a critical role in As-hyperaccumulation by P. vittata, which helps to further improve its utility in phytoremediation of As-contaminated soils.


Assuntos
Arsênio , Pteris , Poluentes do Solo , Arseniato Redutases/genética , Arseniatos , Biodegradação Ambiental , Raízes de Plantas/química , Pteris/genética , Poluentes do Solo/análise
11.
Appl Environ Microbiol ; 86(21)2020 10 15.
Artigo em Inglês | MEDLINE | ID: mdl-32859593

RESUMO

Arsenate is a notorious toxicant that is known to disrupt multiple biochemical pathways. Many microorganisms have developed mechanisms to detoxify arsenate using the ArsC-type arsenate reductase, and some even use arsenate as a terminal electron acceptor for respiration involving arsenate respiratory reductase (Arr). ArsC-type reductases have been studied extensively, but the phylogenetically unrelated Arr system is less investigated and has not been characterized from Archaea Here, we heterologously expressed the genes encoding Arr from the crenarchaeon Pyrobaculum aerophilum in the euryarchaeon Pyrococcus furiosus, both of which grow optimally near 100°C. Recombinant P. furiosus was grown on molybdenum (Mo)- or tungsten (W)-containing medium, and two types of recombinant Arr enzymes were purified, one containing Mo (Arr-Mo) and one containing W (Arr-W). Purified Arr-Mo had a 140-fold higher specific activity in arsenate [As(V)] reduction than Arr-W, and Arr-Mo also reduced arsenite [As(III)]. The P. furiosus strain expressing Arr-Mo (the Arr strain) was able to use arsenate as a terminal electron acceptor during growth on peptides. In addition, the Arr strain had increased tolerance compared to that of the parent strain to arsenate and also, surprisingly, to arsenite. Compared to the parent, the Arr strain accumulated intracellularly almost an order of magnitude more arsenic when cells were grown in the presence of arsenite. X-ray absorption spectroscopy (XAS) results suggest that the Arr strain of P. furiosus improves its tolerance to arsenite by increasing production of less-toxic arsenate and nontoxic methylated arsenicals compared to that by the parent.IMPORTANCE Arsenate respiratory reductases (Arr) are much less characterized than the detoxifying arsenate reductase system. The heterologous expression and characterization of an Arr from Pyrobaculum aerophilum in Pyrococcus furiosus provides new insights into the function of this enzyme. From in vivo studies, production of Arr not only enabled P. furiosus to use arsenate [As(V)] as a terminal electron acceptor, it also provided the organism with a higher resistance to arsenate and also, surprisingly, to arsenite [As(III)]. In contrast to the tungsten-containing oxidoreductase enzymes natively produced by P. furiosus, recombinant P. aerophilum Arr was much more active with molybdenum than with tungsten. It is also, to our knowledge, the only characterized Arr to be active with both molybdenum and tungsten in the active site.


Assuntos
Proteínas Arqueais/genética , Arseniato Redutases/genética , Regulação da Expressão Gênica em Archaea , Pyrococcus furiosus/genética , Thermoproteaceae/genética , Proteínas Arqueais/metabolismo , Arseniato Redutases/metabolismo , Arsênio/metabolismo , Microrganismos Geneticamente Modificados/enzimologia , Microrganismos Geneticamente Modificados/genética , Microrganismos Geneticamente Modificados/metabolismo , Pyrococcus furiosus/enzimologia , Pyrococcus furiosus/metabolismo
12.
Biochim Biophys Acta Bioenerg ; 1861(10): 148252, 2020 10 01.
Artigo em Inglês | MEDLINE | ID: mdl-32569664

RESUMO

The three presently known enzymes responsible for arsenic-using bioenergetic processes are arsenite oxidase (Aio), arsenate reductase (Arr) and alternative arsenite oxidase (Arx), all of which are molybdoenzymes from the vast group referred to as the Mo/W-bisPGD enzyme superfamily. Since arsenite is present in substantial amounts in hydrothermal environments, frequently considered as vestiges of primordial biochemistry, arsenite-based bioenergetics has long been predicted to be ancient. Conflicting scenarios, however, have been put forward proposing either Arr/Arx or Aio as operating in the ancestral metabolism. Phylogenetic data argue in favor of Aio whereas biochemical and physiological data led several authors to propose Arx/Arr as the most ancient anaerobic arsenite metabolizing enzymes. Here we combine phylogenetic approaches with physiological and biochemical experiments to demonstrate that the Arx/Arr enzymes could not have been functional in the Archaean geological eon. We propose that Arr reacts with menaquinones to reduce arsenate whereas Arx reacts with ubiquinone to oxidize arsenite, in line with thermodynamic considerations. The distribution of the quinone biosynthesis pathways, however, clearly indicates that the ubiquinone pathway is recent. An updated phylogeny of Arx furthermore reinforces the hypothesis of a recent emergence of this enzyme. We therefore conclude that anaerobic arsenite redox conversion in the Archaean must have been performed in a metabolism involving Aio.


Assuntos
Arseniato Redutases/metabolismo , Arsenitos/metabolismo , Evolução Molecular , Oxirredutases/metabolismo , Filogenia , Arseniato Redutases/genética , Genômica , Oxirredução , Oxirredutases/genética , Termodinâmica
13.
Sci Total Environ ; 719: 137183, 2020 Jun 01.
Artigo em Inglês | MEDLINE | ID: mdl-32120093

RESUMO

A number of arsenate-reducing bacteria respire adsorbed As(V), producing As(III) and thus contributing to arsenic mobilization from the solid phase to the aqueous phase. Two arsenate reducing genes, arsC and arrA, were both amplified in an indigenous bacterium Bacillus XZM isolated from high arsenic aquifer sediments. The effect of phosphate input on this novel bacterium in terms of mediating the biogeochemical behavior of arsenic was investigated for the first time. The results show bacterial growth and arsenate reduction appear to increase with the addition of phosphate. Input of 1 mM phosphate reduced the negative effects of As(V) on bacterial growth, resulting in 55-60% greater biomass production compared to lower phosphate inputs (0.01 and 0.1 mM). The data of real-time quantitative PCR (qPCR) indicated arsenate was involved in the expressions of two arsenate reductase genes (arsC and arrA genes) in indigenous bacterium Bacillus XZM. Overall, the addition of phosphate (from 0.1 to 1 mM) resulted in a doubling of arsenate bio-desorption from the sediment into the aqueous medium. Oxidation-reduction potential, as an environmental indicator of the bacterial reduction of metals, declined to -200 mV in the presence of strain XZM and 1 mM phosphate in the microcosm. Phosphate input enhanced arsenic biomigration, indicating the effect of phosphate concentration should be considered when studying the biogeochemical behavior of arsenic.


Assuntos
Bacillus , Arseniato Redutases , Arseniatos , Arsênio , Bactérias , Fosfatos
14.
Ecotoxicol Environ Saf ; 195: 110480, 2020 Jun 01.
Artigo em Inglês | MEDLINE | ID: mdl-32203774

RESUMO

Arsenic (As) is a serious threat for environment and human health. Rice, the main staple crop is more prone to As uptake. Bioremediation strategies with heavy metal tolerant rhizobacteria are well known. The main objective of the study was to characterize arsenic-resistant yeast strains, capable of mitigating arsenic stress in rice. Three yeast strains identified as Debaryomyces hansenii (NBRI-Sh2.11), Candida tropicalis (NBRI-B3.4) and Candida dubliniensis (NBRI-3.5) were found to have As reductase activity. D. hansenii with higher As tolerance has As expulsion ability as compared to other two strains. Inoculation of D. hansenii showed improved detoxification through scavenging of reactive oxygen species (ROS) by the modulation of SOD and APX activity under As stress condition in rice. Modulation of defense responsive gene (NADPH, GST, GR) along with arsR and metal cation transporter are the probable mechanism of As detoxification as evident with improved membrane (electrolyte leakage) stability. Reduced grain As (~40% reduction) due to interaction with D. hansenii (NBRI-Sh2.11) further validated it's As mitigation property in rice. To the best of our knowledge D. hansenii has been reported for the first time for arsenic stress mitigation in rice with improved growth and nutrient status of the plant.


Assuntos
Arsênio/toxicidade , Debaryomyces/enzimologia , Oryza/efeitos dos fármacos , Inoculantes Agrícolas , Arseniato Redutases/metabolismo , Arsênio/metabolismo , Biodegradação Ambiental , Candida/enzimologia , Debaryomyces/efeitos dos fármacos , Debaryomyces/genética , Debaryomyces/metabolismo , Oryza/crescimento & desenvolvimento , Espécies Reativas de Oxigênio/metabolismo
15.
J Environ Sci Health B ; 55(5): 447-454, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-31941390

RESUMO

The genome of Acidiphilium multivorum strain AIU 301, acidophilic, aerobic Gram-negative bacteria, was investigated for potential metabolic pathways associated with organic acid production and metal uptake. The genome was compared to other acidic mine drainage isolates, Acidiphilium cryptum JF-5 and Acidithiobacillus ferrooxidans ATCC 23270, as well as Acetobacter pasteurianus 386B, which ferments cocoa beans. Plasmids between two Acidiphilium spp. were compared, and only two of the sixteen plasmids were identified as potentially similar. Comparisons of the genome size to the number of protein coding sequences indicated that A. multivorum and A. cryptum follow the line of best fit unlike A. pasteurianus 386B, which suggests that it was improperly annotated in the database. Pathways between these four species were analyzed bioinformatically and are discussed here. A. multivorum AIU 301, shares pathways with A. pasteurianus 386B including aldehyde and alcohol dehydrogenase pathways, which are used in the generation of vinegar. Mercury reductase, arsenate reductase and sulfur utilization proteins were identified and discussed at length. The absence of sulfur utilization proteins from A. multivorum AIU 301 suggests that this species uses previously undefined pathways for sulfur acquisition. Bioinformatic examination revealed novel pathways that may benefit commercial fields including acetic acid production and biomining.


Assuntos
Ácido Acético/metabolismo , Acidiphilium/genética , Genoma Bacteriano , Acidiphilium/metabolismo , Arseniato Redutases/genética , Biologia Computacional , Simulação por Computador , Tamanho do Genoma , Redes e Vias Metabólicas/genética , Metais/metabolismo , Mineração , Oxirredutases/genética , Plasmídeos , Enxofre/metabolismo
16.
Environ Sci Technol ; 53(24): 14604-14611, 2019 12 17.
Artigo em Inglês | MEDLINE | ID: mdl-31747260

RESUMO

Although arsenic at a high concentration imposes strong selective pressure on microbes, various microbes have been found to grow in As-rich environments. So far, little is known about how microbes can sense and move toward arsenate in the environment, and the underlying molecular mechanisms have not been revealed. Here, we report the chemotaxis response toward arsenate (As(V)) by Shewanella putrefaciens CN-32, a model dissimilatory metal-reducing bacterium (DMRB), and elucidate the mechanisms. We find that S. putrefaciens CN-32 exhibits a chemotactic behavior toward As(V) and diverse electron acceptors. To sense As(V), S. putrefaciens CN-32 requires functional arsenate respiratory reductase but does not depend on its metal-reducing-like respiratory pathway. We observe that such a sense is governed by an energy taxis mechanism and mediated by several methyl-accepting chemotaxis proteins (MCPs), rather than a specific MCP. Moreover, we reveal that the chemotactic signal transduction pathway is conserved in Shewanella, and histidine kinase and flagella-mediated motility are essential for taxis toward As(V). This work reverses the conventional view about arsenic as a chemotactic inhibitor to microbes by revealing the positive chemotaxis of Shewanella to As(V).


Assuntos
Arsênio , Shewanella putrefaciens , Shewanella , Arseniato Redutases , Arseniatos
17.
Sci Signal ; 12(609)2019 11 26.
Artigo em Inglês | MEDLINE | ID: mdl-31772124

RESUMO

The yeast stress-activated protein kinase Hog1 is best known for its role in mediating the response to osmotic stress, but it is also activated by various mechanistically distinct environmental stressors, including heat shock, endoplasmic reticulum stress, and arsenic. In the osmotic stress response, the signal is sensed upstream and relayed to Hog1 through a kinase cascade. Here, we identified a mode of Hog1 function whereby Hog1 senses arsenic through a direct physical interaction that requires three conserved cysteine residues located adjacent to the catalytic loop. These residues were essential for Hog1-mediated protection against arsenic, were dispensable for the response to osmotic stress, and promoted the nuclear localization of Hog1 upon exposure of cells to arsenic. Hog1 promoted arsenic detoxification by stimulating phosphorylation of the transcription factor Yap8, promoting Yap8 nuclear localization, and stimulating the transcription of the only known Yap8 targets, ARR2 and ARR3, both of which encode proteins that promote arsenic efflux. The related human kinases ERK1 and ERK2 also bound to arsenic in vitro, suggesting that this may be a conserved feature of some members of the mitogen-activated protein kinase (MAPK) family. These data provide a mechanistic basis for understanding how stress-activated kinases can sense distinct threats and perform highly specific adaptive responses.


Assuntos
Arsênio/farmacologia , Sistema de Sinalização das MAP Quinases/efeitos dos fármacos , Proteínas Quinases Ativadas por Mitógeno/metabolismo , Proteínas de Saccharomyces cerevisiae/metabolismo , Saccharomyces cerevisiae/metabolismo , Arseniato Redutases/genética , Arseniato Redutases/metabolismo , Fatores de Transcrição de Zíper de Leucina Básica/genética , Fatores de Transcrição de Zíper de Leucina Básica/metabolismo , Sistema de Sinalização das MAP Quinases/genética , Proteínas Quinases Ativadas por Mitógeno/genética , Saccharomyces cerevisiae/genética , Proteínas de Saccharomyces cerevisiae/genética
18.
NPJ Syst Biol Appl ; 5: 28, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31428455

RESUMO

To study systems-level properties of the cell, it is necessary to go beyond individual regulators and target genes to study the regulatory network among transcription factors (TFs). However, it is difficult to directly dissect the TFs mediated genome-wide gene regulatory network (GRN) by experiment. Here, we proposed a hierarchical graphical model to estimate TF activity from mRNA expression by building TF complexes with protein cofactors and inferring TF's downstream regulatory network simultaneously. Then we applied our model on flower development and circadian rhythm processes in Arabidopsis thaliana. The computational results show that the sequence specific bHLH family TF HFR1 recruits the chromatin regulator HAC1 to flower development master regulator TF AG and further activates AG's expression by histone acetylation. Both independent data and experimental results supported this discovery. We also found a flower tissue specific H3K27ac ChIP-seq peak at AG gene body and a HFR1 motif in the center of this H3K27ac peak. Furthermore, we verified that HFR1 physically interacts with HAC1 by yeast two-hybrid experiment. This HFR1-HAC1-AG triplet relationship may imply that flower development and circadian rhythm are bridged by epigenetic regulation and enrich the classical ABC model in flower development. In addition, our TF activity network can serve as a general method to elucidate molecular mechanisms on other complex biological regulatory processes.


Assuntos
Proteínas de Arabidopsis/genética , Proteínas de Arabidopsis/metabolismo , Biologia Computacional/métodos , Proteínas de Ligação a DNA/genética , Proteínas de Ligação a DNA/metabolismo , Proteína AGAMOUS de Arabidopsis/genética , Proteína AGAMOUS de Arabidopsis/metabolismo , Arabidopsis/genética , Arabidopsis/metabolismo , Arseniato Redutases/metabolismo , Ritmo Circadiano/genética , Ritmo Circadiano/fisiologia , Epigênese Genética/genética , Flores/genética , Regulação da Expressão Gênica de Plantas/genética , Redes Reguladoras de Genes , Genoma , Proteínas Nucleares/genética , Fatores de Transcrição/genética , Fatores de Transcrição/metabolismo
19.
Plant Cell ; 31(9): 2187-2205, 2019 09.
Artigo em Inglês | MEDLINE | ID: mdl-31320481

RESUMO

Groucho/Thymidine uptake 1 (Gro/Tup1) family proteins are evolutionarily conserved transcriptional coregulators in eukaryotic cells. Despite their prominent function in transcriptional repression, little is known about their role in transcriptional activation and the underlying mechanism. Here, we report that the plant Gro/Tup1 family protein LEUNIG_HOMOLOG (LUH) activates MYELOCYTOMATOSIS2 (MYC2)-directed transcription of JAZ2 and LOX2 via the Mediator complex coactivator and the histone acetyltransferase HAC1. We show that the Mediator subunit MED25 physically recruits LUH to MYC2 target promoters that then links MYC2 with HAC1-dependent acetylation of Lys-9 of histone H3 (H3K9ac) to activate JAZ2 and LOX2 Moreover, LUH promotes hormone-dependent enhancement of protein interactions between MYC2 and its coactivators MED25 and HAC1. Our results demonstrate that LUH interacts with MED25 and HAC1 through its distinct domains, thus imposing a selective advantage by acting as a scaffold for MYC2 activation. Therefore, the function of LUH in regulating jasmonate signaling is distinct from the function of TOPLESS, another member of the Gro/Tup1 family that represses MYC2-dependent gene expression in the resting stage.


Assuntos
Proteínas de Arabidopsis/metabolismo , Arabidopsis/metabolismo , Arseniato Redutases/metabolismo , Fatores de Transcrição de Zíper de Leucina e Hélice-Alça-Hélix Básicos/metabolismo , Proteínas de Ligação a DNA/metabolismo , Ativação Transcricional/fisiologia , Acetilação , Arabidopsis/genética , Proteínas de Arabidopsis/genética , Arseniato Redutases/genética , Fatores de Transcrição de Zíper de Leucina e Hélice-Alça-Hélix Básicos/genética , Proteínas de Ligação a DNA/genética , Regulação da Expressão Gênica de Plantas , Histonas , Lipoxigenases/genética , Lipoxigenases/metabolismo , Plantas Geneticamente Modificadas , Regiões Promotoras Genéticas , Proteínas Repressoras/genética , Proteínas Repressoras/metabolismo , Transdução de Sinais/genética , Fatores de Transcrição/genética , Fatores de Transcrição/metabolismo , Transcrição Genética , Ativação Transcricional/genética
20.
Arch Microbiol ; 201(9): 1285-1293, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31256199

RESUMO

Aiming at revealing the arsenic (As) resistance of the endophytic Kocuria strains isolated from roots and stems of Sphaeralcea angustifolia grown at mine tailing, four strains belonging to different clades of Kocuria based upon the phylogeny of 16S rRNA genes were screened for minimum inhibitory concentration (MIC). Only the strain NE1RL3 was defined as an As-resistant bacterium with MICs of 14.4/0.0125 mM and 300/20.0 mM for As3+ and As5+, respectively, in LB/mineral media. This strain was identified as K. palustris based upon analyses of cellular chemical compositions (cellular fatty acids, isoprenoides, quinones, and sugars), patterns of carbon source, average nucleotide identity of genome and digital DNA-DNA relatedness. Six genes coding to enzymes or proteins for arsenate reduction and arsenite-bumping were detected in the genome, demonstrating that this strain is resistant to As possibly by reducing As5+ to As3+, and then bumping As3+ out of the cell. However, this estimation was not confirmed since no arsenate reduction was detected in a subsequent assay. This study reported for the first time the presence of phylogenetically distinct arsenate reductase genes in a Kocuria strain and evidenced the possible horizontal transfer of these genes among the endophytic bacteria.


Assuntos
Arseniato Redutases/genética , Arseniatos/metabolismo , Micrococcaceae/enzimologia , Micrococcaceae/genética , Arsênio/farmacologia , Arsenitos/metabolismo , Testes de Sensibilidade Microbiana , Micrococcaceae/metabolismo , Filogenia , RNA Ribossômico 16S/genética , Traqueófitas/microbiologia
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