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1.
Environ Pollut ; 312: 120085, 2022 Nov 01.
Artículo en Inglés | MEDLINE | ID: mdl-36058313

RESUMEN

Bacteria are candidates for the biotransformation of environmental arsenic (As), while As metabolism in bacteria is not yet fully understood. In this study, we sequenced the genome of an As-resistant bacterium strain Stenotrophomonas maltophilia SCSIOOM isolated from the fish gut. After arsenate (As(V)) exposure, S. maltophilia transformed As(V) to organoarsenicals, along with the significant change of the expression of 40 genes, including the upregulation of arsH, arsRBC and betIBA. The heterogeneous expression of arsH and arsRBC increased As resistance of E. coli AW3110 by increasing As efflux and transformation. E. coli AW3110 (pET-betIBA) could transform inorganic As into dimethylarsinate (DMA) and nontoxic arsenobetaine (AsB), which suggested that AsB could be synthesized through the synthetic pathway of its analog-glycine betaine. In addition, the existence of arsRBC, betIBA and arsH reduced the reactive oxygen species (ROS) induced by As exposure. In total, these results demonstrated that S. maltophilia adopted an As metabolism strategy by reducing As accumulation and synthesizing less toxic As species. We first reported the production and potential synthetic pathway of AsB in bacteria, which improved our knowledge of As toxicology in microorganisms.


Asunto(s)
Arsénico , Stenotrophomonas maltophilia , Animales , Arseniatos/metabolismo , Arseniatos/toxicidad , Arsénico/metabolismo , Arsénico/toxicidad , Arsenicales , Betaína/metabolismo , Ácido Cacodílico/metabolismo , Escherichia coli/metabolismo , Peces/metabolismo , Especies Reactivas de Oxígeno/metabolismo , Stenotrophomonas maltophilia/metabolismo
2.
Cells ; 11(17)2022 Sep 02.
Artículo en Inglés | MEDLINE | ID: mdl-36078150

RESUMEN

Arsenic (As) is a toxic metalloid for all living organisms and can cause serious harm to humans. Arsenic is also toxic to plants. To alleviate As toxicity, all living organisms (from prokaryotes to higher plants) have evolved comprehensive mechanisms to reduce cytosolic As concentration through the set of As transporters localized at the plasma and tonoplast membranes, which operate either in arsenite As(III) extrusion out of cells (via ArsB, ACR3, and aquaporins) or by sequestering arsenic into vacuoles (by ABC transporters). In addition, a special arsenate resistance mechanism found in some bacterial systems has evolved in an As hyperaccumulating fern Pteris vittata, which involves transforming arsenate As(V) to an As(V) phosphoglycerate derivative by a glyceraldehyde 3-phosphate dehydrogenase and transporting this complex by an efflux transporter. In the present review, we summarize the evolution of these arsenic resistance mechanisms from prokaryotes to eukaryotes and discuss future approaches that could be utilized to better understand and improve As resistance mechanisms in plants.


Asunto(s)
Arsénico , Pteris , Arseniatos/metabolismo , Arsénico/metabolismo , Arsénico/toxicidad , Humanos , Proteínas de Transporte de Membrana , Pteris/metabolismo , Vacuolas/metabolismo
3.
Environ Pollut ; 312: 120040, 2022 Nov 01.
Artículo en Inglés | MEDLINE | ID: mdl-36030950

RESUMEN

Arsenite (As(III)) is more toxic, mobilizable and bioavailable than arsenate (As(V)). Hence, the transformations between As(III) and As(V) are crucial for the toxicity and mobility of arsenic (As). However, As transformation and microbial communities involved in alkaline soils are largely unknown. Here we investigate two major pathways of As transformation, i.e., As(III) oxidation and As(V) reduction, and identify the bacteria involved in the alkaline soil by combining stable isotope probing with shotgun metagenomic sequencing. As(III) oxidation and significant increase of the aioA genes copies were observed in the treatments amended with As(III) and NO3-, suggesting that As(III) oxidation can couple with nitrate reduction and was mainly catalyzed by the microorganisms containing aioA genes. As(V) reduction was detected in the treatments amended with As(V) and acetate where the abundance of arrA gene significantly increased, indicating that microorganisms with arrA genes were the key As(V) reducers. Acidovorax, Hydrogenophaga, and Ramlibacter were the putative nitrate-dependent As(III) oxidizers, and Deinococcus and Serratia were the putative respiratory As(V) reducers. These findings will improve our understanding of As metabolism and are meaningful for mapping out bioremediation strategies of As contamination in alkaline environment.


Asunto(s)
Arsénico , Arsenitos , Arseniatos/metabolismo , Arsénico/metabolismo , Arsenitos/metabolismo , Bacterias/genética , Bacterias/metabolismo , Isótopos/metabolismo , Nitratos/metabolismo , Oxidación-Reducción , Suelo , Microbiología del Suelo
4.
Ecotoxicol Environ Saf ; 242: 113856, 2022 Sep 01.
Artículo en Inglés | MEDLINE | ID: mdl-35809392

RESUMEN

Arsenic (As) and lead (Pb) are frequently emitted from various sources into environment, but microbial responses to their combined toxicity have not been systematically investigated. In this study, Chlamydomonas reinhardtii was exposed to two levels of arsenate (As (V), 50, 500 µg/L), Pb (II) (500, 5000 µg/L) and their mixture (50 µg/L As (V) + 500 µg/L Pb (II); 500 µg/L As (V) + 5000 µg/L Pb (II)). The growth of C. reinhardtii was inhibited more remarkably by As (V) than by Pb (II). The As stress was alleviated by Pb in the 50 µg/L As (V) + 500 µg/L Pb (II) treatment, but was enhanced upon the 500 µg/L As (V) + 5000 µg/L Pb (II) exposure, with more pronounced changes in a number of physiological parameters of the algal cells. Proteomic results showed that 71 differently expressed proteins (DEPs) in the treatment of 50 µg/L As (V) + 500 µg/L Pb (II), and 167 DEPs were identified in that of 500 µg/L As (V) + 5000 µg/L Pb (II). These proteins were involved in energy metabolism, photosynthetic carbon fixation, reactive oxygen scavenging and defense, and amino acid synthesis. Taken together, these physiological and proteomic data demonstrated that C. reinhardtii could resist the As (V) and Pb (II) combined treatments through extracellular complexation and intracellular pathways.


Asunto(s)
Arsénico , Chlamydomonas reinhardtii , Arseniatos/metabolismo , Arseniatos/toxicidad , Arsénico/metabolismo , Chlamydomonas reinhardtii/metabolismo , Plomo/metabolismo , Plomo/toxicidad , Proteómica/métodos
5.
Environ Pollut ; 308: 119698, 2022 Sep 01.
Artículo en Inglés | MEDLINE | ID: mdl-35787423

RESUMEN

Dissimilatory arsenate-respiring prokaryotes (DARPs) are considered to be the major drive of the reductive mobilization of arsenic from solid phases. However, it is not fully understood how phosphate, a structural analog of arsenate, affects the DARPs-mediated arsenic mobilization. This work aimed to address this issue. As-contaminated soils were collected from a Shimen Realgar Mine-affected area. We identified a unique diversity of DARPs from the soils, which possess high As(V)-respiring activities using one of multiple small organic acids as the electron donor. After elimination of the desorption effect of phosphate on the As mobilization, the supplement of additional 10 mM phosphate to the active slurries markedly increased the microbial community-mediated reductive mobilization of arsenic as revealed by microcosm tests; this observation was associated to the fact that phosphate significantly increased the As(V)-respiratory reductase (Arr) gene abundances in the slurries. To confirm this finding, we further obtained a new DARP strain, Priestia sp. F01, from the samples. We found that after elimination of the chemical effect of phosphate, the supplement of 10 mM phosphate to the active slurries resulted in an 82.2% increase of the released As(III) in the solutions, which could be contributed to that excessive phosphate greatly increased the Arr gene abundance, and enhanced the transcriptional level of arrA gene and the bacterial As(V)-respiring activity of F01 cells. Considering that phosphate commonly coexists with As in the environment, and is a frequently-used fertilizer, these findings are helpful for deeply understanding why As concentrations in contaminated groundwater are dynamically fluctuated, and also provided new knowledge on the interactions between the biogeochemical processes of P and As.


Asunto(s)
Arsénico , Agua Subterránea , Arseniatos/metabolismo , Arsénico/metabolismo , Bacterias/metabolismo , Catálisis , Agua Subterránea/química , Fosfatos/metabolismo , Suelo/química
6.
Aquat Toxicol ; 249: 106218, 2022 Aug.
Artículo en Inglés | MEDLINE | ID: mdl-35704967

RESUMEN

Arsenic pollution in freshwater poses a serious threat to aquatic organisms. However, dissolved organic matter (DOM) in water can modulate arsenic environmental toxicity by either suppressing or promoting its bioaccumulation. In this study, we investigated the toxicity, bioaccumulation, and biotransformation of inorganic arsenic (arsenite AsIII and arsenate AsV) combined with two types of DOM, i.e., humic acid (HA) and fulvic acid (FA), in the algae Chlamydomonas reinhardtii and Ochromonas danica. C. reinhardtii has a cell wall and cannot bioaccumulate arsenic complexation, whereas O. danica has no cell wall. Without DOM, AsV was more toxic than AsIII for C. reinhardtii, and AsV was less toxic than AsIII for O. danica. HA and FA addition reduced AsV and AsIII toxicities; the larger molecular weight (Mw) of HA contributed to the reduction in toxicity to an even greater extent, and reduced arsenic accumulation while promoting the biotransformation ability of C. reinhardtii, which has a cell wall. However, HA and FA addition increased AsV and AsIII toxicities and arsenic accumulation while relatively enhancing the biotransformation ability of O. danica, which has no cell wall. Coupling toxicity, bioaccumulation, and biotransformation, DOM (HA and FA) contributed to the altered toxicity of freshwater algae to AsV and AsIII through reduced/increased arsenic accumulation and enhanced biotransformation. Overall, our study considered the combined toxicity of inorganic arsenic and DOM in phytoplankton, helping estimate the potential environmental risk of arsenic in aqueous environments.


Asunto(s)
Arsénico , Arsenicales , Arsenitos , Contaminantes Químicos del Agua , Arseniatos/metabolismo , Arseniatos/toxicidad , Arsénico/toxicidad , Arsenitos/metabolismo , Arsenitos/toxicidad , Biotransformación , Agua Dulce , Sustancias Húmicas , Contaminantes Químicos del Agua/toxicidad
7.
Environ Pollut ; 307: 119320, 2022 Aug 15.
Artículo en Inglés | MEDLINE | ID: mdl-35490999

RESUMEN

The growth and development patterns of crop plants are being seriously threatened by arsenic (As) contamination in the soil, and it also acts as a major hurdle in crop productivity. This study focuses on arsenate As(V) mediated toxicity in rice plants. Further, among the different type of NPs, iron oxide nanoparticles (FeO NPs) display a dose-dependent effect but their potential role in mitigating As(V) stress is still elusive. FeO NPs (500 µM) play a role in imparting cross-tolerance against As(V) induced toxicity in rice. Growth attributes, photosynthetic performance, nutrient contents and biochemical parameters were significantly altered by As(V). But FeO NPs rescued the negative consequences of As(V) by restricting its entry with the possible involvement of NO in rice roots. Moreover, results related with gene expression of NO(OsNoA1 and OsNIA1) and proline metabolism were greatly inhibited by As(V) toxicity. But, FeO NPs reversed the toxic effect of As(V) by improving proline metabolism and stimulating NO mediated up-regulation of antioxidant enzymes particularly glutathione-S-transferase which may be possible reasons for the reduction of As(V) toxicity in rice roots. Overall, it can be stated that FeO NPs may act as an As(V) barrier to restrict the As(V) uptake by roots and have the ability to confer cross tolerance by modulating various morphological, biochemical and molecular characteristics with possible intrinsic involvement of NO.


Asunto(s)
Arsénico , Oryza , Arseniatos/metabolismo , Arseniatos/toxicidad , Arsénico/metabolismo , Nanopartículas Magnéticas de Óxido de Hierro , Óxido Nítrico/metabolismo , Oryza/metabolismo , Raíces de Plantas/metabolismo , Prolina/metabolismo , Prolina/farmacología , Plantones
8.
Environ Pollut ; 306: 119451, 2022 Aug 01.
Artículo en Inglés | MEDLINE | ID: mdl-35569621

RESUMEN

Bacteria play crucial roles in the biogeochemical cycle of arsenic (As) and selenium (Se) as these elements are metabolized via detoxification, energy generation (anaerobic respiration) and biosynthesis (e.g. selenocysteine) strategies. To date, arsenic and selenium biomineralization in bacteria were studied separately. In this study, the anaerobic metabolism of As and Se in Shewanella sp. O23S was investigated separately and mixed, with an emphasis put on the biomineralization products of this process. Multiple analytical techniques including ICP-MS, TEM-EDS, XRD, Micro-Raman, spectrophotometry and surface charge (zeta potential) were employed. Shewanella sp. O23S is capable of reducing selenate (SeO42-) and selenite (SeO32-) to red Se(-S)0, and arsenate (AsO43-) to arsenite (AsO33-). The release of H2S from cysteine led to the precipitation of AsS minerals: nanorod AsS and granular As2S3. When As and Se oxyanions were mixed, both As-S and Se(-S)0 biominerals were synthesized. All biominerals were extracellular, amorphous and presented a negative surface charge (-24 to -38 mV). Kinetic analysis indicated the following reduction yields: SeO32- (90%), AsO43- (60%), and SeO42- (<10%). The mix of SeO32- with AsO43- led to a decrease in As removal to 30%, while Se reduction yield was unaffected (88%). Interestingly, SeO42- incubated with AsO43- boosted the Se removal (71%). The exclusive extracellular formation of As and Se biominerals might indicate an extracellular respiratory process characteristic of various Shewanella species and strains. This is the first study documenting a complex interplay between As and Se oxyanions: selenite decreased arsenate reduction, whereas arsenate stimulated selenate reduction. Further investigation needs to clarify whether Shewanella sp. O23S employs multi-substrate respiratory enzymes or separate, high affinity enzymes for As and Se oxyanion respiration.


Asunto(s)
Arsénico , Compuestos de Selenio , Selenio , Shewanella , Arseniatos/metabolismo , Arsénico/metabolismo , Biomineralización , Cinética , Ácido Selénico , Ácido Selenioso , Selenio/metabolismo , Shewanella/metabolismo
9.
Environ Sci Pollut Res Int ; 29(47): 70862-70881, 2022 Oct.
Artículo en Inglés | MEDLINE | ID: mdl-35589895

RESUMEN

A green house experiment was conducted to evaluate the efficacy of soil application of selenium (Se) in modulating metabolic changes in rice under arsenic (As) stress. Rice plants were grown over soil amended with sodium arsenate (25, 50 and 100 µM kg-1 soil) with or without sodium selenate @ 0.5 and 1 mg kg-1 soil in a complete randomized experimental design, and photosynthetic efficiency, nutrient uptake and nitrogen metabolism in rice leaves were estimated at tillering and grain filling stages. Se treatments significantly improved the toxic effects of As on plant height, leaf dry weight and grain yield. Arsenate treatment reduced uptake of Na, Mg, P, K, Ca, Mn, Fe and Zn and lowered chlorophyll, carotenoids and activities of enzymes of nitrogen metabolism (nitrate reductase, nitrite reductase, glutamine synthase and glutamate synthase) in rice leaves at both the stages in a dose-dependent fashion. Se application along with As improved photosynthesis, nutrient uptake and arsenate-induced effects on activities of enzymes of nitrogen metabolism with maximum impact shown by As50 + Se1 combination. Application of Se can modulate photosynthetic efficiency, nutrient uptake and alterations in nitrogen metabolism in rice Cv PR126 due to As stress that helped plants to adapt to excess As and resulted in improved plant growth.


Asunto(s)
Arsénico , Oryza , Selenio , Arseniatos/metabolismo , Arsénico/metabolismo , Carotenoides/metabolismo , Clorofila/metabolismo , Grano Comestible/metabolismo , Glutamato Sintasa/metabolismo , Glutamina/metabolismo , Glutamina/farmacología , Nitrito Reductasas/metabolismo , Nitrógeno/metabolismo , Nutrientes , Oryza/metabolismo , Fotosíntesis , Hojas de la Planta/metabolismo , Ácido Selénico/metabolismo , Selenio/metabolismo , Selenio/farmacología , Suelo
10.
Environ Sci Pollut Res Int ; 29(41): 62423-62431, 2022 Sep.
Artículo en Inglés | MEDLINE | ID: mdl-35397725

RESUMEN

Iron oxide nanoparticles (nano-Fe2O3) widely distribute in waters with low toxicity to aquatic organisms. But it is unclear for nano-Fe2O3 to affect the fate of coexisting arsenic (As) with its bioaccumulation and biotransformation. In this study, we thus mainly investigated arsenate (As(V)) toxicity, uptake kinetics, biotransformation and subcellular distribution in Microcystis aeruginosa influenced by nano-Fe2O3. The results showed that M. aeruginosa was more sensitive to As(V) associated with nano-Fe2O3. Due to the exaggerated increase of efflux rate constants of As compared with the uptake rate constants in algal cells affected by different levels of nano-Fe2O3, the As(V) bioconcentration factor decreased with nano-Fe2O3 increasing correspondingly, indicating that As bioaccumulation was diminished by nano-Fe2O3. The decreased As accumulation in M. aeruginosa could be supported by the evidential As(V) sequestration through high adsorption of nano-Fe2O3, which resulted in decreasing free As level for algae uptake in media. Meanwhile, As subcellular distribution was adjusted by nano-Fe2O3 with decreasing in cell walls and rising in cytoplasmic organelles compared with nano-Fe2O3 free. As(V) reduction and methylation were enhanced with increasing nano-Fe2O3, stimulating by its sensitivity to the interaction of nano-Fe2O3 and As(V) as well as the rising level of As in cytoplasmic organelles of this algae. It is confirmed by the higher relative gene expression levels of arsC and arsM in elevated nano-Fe2O3. Accordingly, it is highlighted to be deserved more attention that the changing behavior of As(V) by nano-Fe2O3 that reduce As bioaccumulation and accelerate its biotransformation in algae in As contaminated water.


Asunto(s)
Arsénico , Microcystis , Arseniatos/metabolismo , Arsénico/metabolismo , Bioacumulación , Biotransformación , Microcystis/metabolismo
11.
Environ Microbiol ; 24(4): 1977-1987, 2022 04.
Artículo en Inglés | MEDLINE | ID: mdl-35229439

RESUMEN

Arsenical resistance (ars) operons encode genes for arsenic resistance and biotransformation. The majority are composed of individual genes, but fusion of ars genes is not uncommon, although it is not clear if the fused gene products are functional. Here we report identification of a four-gene ars operon from Paracoccus sp. SY that has two arsR-arsC gene fusions. ArsRC1 and ArsRC2 are related proteins that consist of an N-terminal ArsR arsenite (As(III))-responsive repressor with a C-terminal ArsC arsenate reductase. The other two genes in the operon are gapdh and arsJ. GAPDH, glyceraldehyde 3-phosphate dehydrogenase, forms 1-arseno-3-phosphoglycerate (1As3PGA) from 3-phosphoglyceraldehyde and arsenate (As(V)), ArsJ is an efflux permease for 1As3PGA that dissociates into extracellular As(V) and 3-phosphoglycerate. The net effect is As(V) extrusion and resistance. ArsRs are usually selective for As(III) and do not respond to As(V). However, the substrates and products of this operon are pentavalent, which would not be inducers of the operon. We propose that ArsRC fusions overcome this limitation by channelling the ArsC product into the ArsR binding site without diffusion through the cytosol, a de facto mechanism for As(V) induction. This novel mechanism for arsenate sensing can confer an evolutionary advantage for detoxification of inorganic arsenate.


Asunto(s)
Arsénico , Arsenicales , Arsenitos , Arseniatos/metabolismo , Arsénico/metabolismo , Arsenicales/metabolismo , Arsenitos/metabolismo , Proteínas Bacterianas/genética , Proteínas Bacterianas/metabolismo , Regulación Bacteriana de la Expresión Génica , Operón
12.
J Hazard Mater ; 431: 128532, 2022 06 05.
Artículo en Inglés | MEDLINE | ID: mdl-35248958

RESUMEN

A comparative analysis of toxicities of both arsenic forms (arsenite and arsenate) in the model eukaryotic microorganism Tetrahymena thermophila (ciliate protozoa) has shown the presence of various detoxification mechanisms and cellular effects comparable to those of animal cells under arsenic stress. In the wild type strain SB1969 arsenate is almost 2.5 times more toxic than arsenite. According to the concentration addition model used in binary metallic mixtures their toxicities show an additive effect. Using fluorescent assays and flow cytometry, it has been detected that As(V) generates elevated levels of ROS/RNS compared to As(III). Both produce the same levels of superoxide anion, but As(V) also causes greater increases in hydrogen peroxide and peroxynitrite. The mitochondrial membrane potential is affected by both As(V) and As(III), and electron microscopy has also revealed that mitochondria are the main target of both arsenic ionic forms. Fusion/fission and swelling mitochondrial and mitophagy, together with macroautophagy, vacuolization and mucocyst extruction are mainly associated to As(V) toxicity, while As(III) induces an extensive lipid metabolism dysfunction (adipotropic effect). Quantitative RT-PCR analysis of some genes encoding antioxidant proteins or enzymes has shown that glutathione and thioredoxin metabolisms are involved in the response to arsenic stress. Likewise, the function of metallothioneins seems to be crucial in arsenic detoxification processes, after using both metallothionein knockout and knockdown strains and cells overexpressing metallothionein genes from this ciliate. The analysis of the differential toxicity of As(III) and As(V) shown in this study provides cytological and molecular tools to be used as biomarkers for each of the two arsenic ionic forms.


Asunto(s)
Arsénico , Arsenitos , Tetrahymena thermophila , Animales , Arseniatos/metabolismo , Arseniatos/toxicidad , Arsénico/metabolismo , Arsénico/toxicidad , Arsenitos/metabolismo , Arsenitos/toxicidad , Metalotioneína , Tetrahymena thermophila/genética
13.
Int J Mol Sci ; 23(4)2022 Feb 18.
Artículo en Inglés | MEDLINE | ID: mdl-35216388

RESUMEN

Phosphorus is an essential macronutrient for plants. The phosphate (Pi) concentration in soil solutions is typically low, and plants always suffer from low-Pi stress. During Pi starvation, a number of adaptive mechanisms in plants have evolved to increase Pi uptake, whereas the mechanisms are not very clear. Here, we report that an ubiquitin E3 ligase, PRU2, modulates Pi acquisition in Arabidopsis response to the low-Pi stress. The mutant pru2 showed arsenate-resistant phenotypes and reduced Pi content and Pi uptake rate. The complementation with PRU2 restored these to wild-type plants. PRU2 functioned as an ubiquitin E3 ligase, and the protein accumulation of PRU2 was elevated during Pi starvation. PRU2 interacted with a kinase CK2α1 and a ribosomal protein RPL10 and degraded CK2α1 and RPL10 under low-Pi stress. The in vitro phosphorylation assay showed that CK2α1 phosphorylated PHT1;1 at Ser-514, and prior reports demonstrated that the phosphorylation of PHT1;1 Ser-514 resulted in PHT1;1 retention in the endoplasmic reticulum. Then, the degradation of CK2α1 by PRU2 under low-Pi stress facilitated PHT1;1 to move to the plasma membrane to increase Arabidopsis Pi uptake. Taken together, this study demonstrated that the ubiquitin E3 ligase-PRU2-was an important positive regulator in modulating Pi acquisition in Arabidopsis response to low-Pi stress.


Asunto(s)
Proteínas de Arabidopsis/metabolismo , Arabidopsis/metabolismo , Transporte Biológico/fisiología , Fosfatos/metabolismo , Ubiquitina-Proteína Ligasas/metabolismo , Arseniatos/metabolismo , Membrana Celular/metabolismo , Regulación de la Expresión Génica de las Plantas/fisiología , Proteínas de Transporte de Fosfato/metabolismo , Fósforo/metabolismo , Plantas Modificadas Genéticamente/metabolismo , Factores de Transcripción/metabolismo , Ubiquitinas/metabolismo
14.
Int J Phytoremediation ; 24(7): 763-777, 2022.
Artículo en Inglés | MEDLINE | ID: mdl-34579603

RESUMEN

This study aims to investigate the potentiality of selenium in modulating arsenic stress in rice seedlings. Arsenate accumulation along with its transformation to arsenite was enhanced in arsenate exposed seedlings. Arsenite induced oxidative stress and severely affected the growth of the seedlings. Arsenate exposure caused an elevation in ascorbate and glutathione levels along with the activities of their metabolizing enzymes viz., ascorbate peroxidase, glutathione reductase, glutathione-S-transferase, and glutathione peroxidase. Phytochelatins content was increased under arsenic stress to subdue the toxic effects in the test seedlings. Co-application of arsenate and selenate in rice seedlings manifested pronounced alteration of oxidative stress, antioxidant defense, and thiol metabolism as compared to arsenate treatment only. ANOVA analysis (Tukey's HSD test) demonstrated the relevance of using selenate along with arsenate to maintain the normal growth and development of rice seedlings. Thus, exogenous supplementation of selenium will be a beneficial approach to cultivate rice seedlings in arsenic polluted soil.


Arsenic toxicity in the environment is a global concern, causes chronic signs of poisoning to plants and humans, leads to ecological imbalance. Selenium is known for its antagonistic characteristics and has been found to be effective in combating the adversities of arsenic at low concentrations (5 µM). The present study was performed to explore the comparative responses of rice seedlings during the joint application of selenium and arsenic in terms of growth, generation of oxidative stress, antioxidant defense, and thiol metabolism. Although the molecular basis of arsenic­selenium interaction is widely known a small number of reports were listed about the physio-chemical role of selenium against arsenic stress. Thus, we investigated the influence of selenium to alleviate arsenic-induced toxic effects by modulating the activities of antioxidant enzymes and reducing the levels of oxidative stress markers. It has been noted that selenium regulates thiol metabolism which is known to play a key role in growth preservation by restriction of arsenic translocation. The outcome from the study would be useful in field trials for sustainable agriculture in arsenic-contaminated soil.


Asunto(s)
Arsénico , Arsenitos , Oryza , Selenio , Antioxidantes/metabolismo , Arseniatos/metabolismo , Arseniatos/toxicidad , Arsénico/metabolismo , Arsénico/toxicidad , Arsenitos/metabolismo , Arsenitos/toxicidad , Biodegradación Ambiental , Glutatión/metabolismo , Glutatión/farmacología , Oryza/metabolismo , Estrés Oxidativo , Plantones , Ácido Selénico/metabolismo , Ácido Selénico/farmacología , Selenio/metabolismo , Selenio/farmacología , Compuestos de Sulfhidrilo/metabolismo
15.
Mol Plant ; 14(9): 1489-1507, 2021 09 06.
Artículo en Inglés | MEDLINE | ID: mdl-34048950

RESUMEN

In nature, plants acquire nutrients from soils to sustain growth, and at the same time, they need to avoid the uptake of toxic compounds and/or possess tolerance systems to cope with them. This is particularly challenging when the toxic compound and the nutrient are chemically similar, as in the case of phosphate and arsenate. In this study, we demonstrated that regulatory elements of the phosphate starvation response (PSR) coordinate the arsenate detoxification machinery in the cell. We showed that arsenate repression of the phosphate transporter PHT1;1 is associated with the degradation of the PSR master regulator PHR1. Once arsenic is sequestered into the vacuole, PHR1 stability is restored and PHT1;1 expression is recovered. Furthermore, we identified an arsenite responsive SKP1-like protein and a PHR1 interactor F-box (PHIF1) as constituents of the SCF complex responsible for PHR1 degradation.We found that arsenite, the form to which arsenate is reduced for compartmentalization in vacuoles, represses PHT1;1 expression, providing a highly selective signal versus phosphate to control PHT1;1 expression in response to arsenate. Collectively, our results provide molecular insights into a sensing mechanism that regulates arsenate/phosphate uptake depending on the plant's detoxification capacity.


Asunto(s)
Proteínas de Arabidopsis/metabolismo , Arseniatos/metabolismo , Factores de Transcripción/metabolismo , Arabidopsis/genética , Arabidopsis/metabolismo , Proteínas de Arabidopsis/genética , Arseniatos/farmacología , Transporte Biológico , Regulación de la Expresión Génica de las Plantas , Proteínas de Transporte de Fosfato/genética , Proteínas de Transporte de Fosfato/metabolismo , Fosfatos/metabolismo , Plantas Modificadas Genéticamente , Factores de Transcripción/genética , Vacuolas/metabolismo
16.
Biometals ; 34(4): 895-907, 2021 08.
Artículo en Inglés | MEDLINE | ID: mdl-33956287

RESUMEN

Bacillus flexus strain SSAI1 isolated from agro-industry waste, Tuem, Goa, India displayed high arsenite resistance as minimal inhibitory concentration was 25 mM in mineral salts medium. This bacterial strain exposed to 10 mM arsenite demonstrated rapid arsenite oxidation and internalization of 7 mM arsenate within 24 h. The Fourier transformed infrared (FTIR) spectroscopy of cells exposed to arsenite revealed important functional groups on the cell surface interacting with arsenite. Furthermore, scanning electron microscopy combined with electron dispersive X-ray spectroscopy (SEM-EDAX) of cells exposed to arsenite revealed clumping of cells with no surface adsorption of arsenite. Transmission electron microscopy coupled with electron dispersive X-ray spectroscopic (TEM-EDAX) analysis of arsenite exposed cells clearly demonstrated ultra-structural changes and intracellular accumulation of arsenic. Whole-genome sequence analysis of this bacterial strain interestingly revealed the presence of large number of metal(loid) resistance genes, including aioAB genes encoding arsenite oxidase responsible for the oxidation of highly toxic arsenite to less toxic arsenate. Enzyme assay further confirmed that arsenite oxidase is a periplasmic enzyme. The genome of strain SSAI1 also carried glpF, aioS and aioE genes conferring resistance to arsenite. Therefore, multi-metal(loid) resistant arsenite oxidizing Bacillus flexus strain SSAI1 has potential to bioremediate arsenite contaminated environmental sites and is the first report of its kind.


Asunto(s)
Arseniatos/farmacología , Arsenitos/farmacología , Bacillus/efectos de los fármacos , Proteínas Bacterianas/metabolismo , Oxidorreductasas/metabolismo , Arseniatos/metabolismo , Arsenitos/metabolismo , Bacillus/crecimiento & desarrollo , Bacillus/metabolismo , Proteínas Bacterianas/genética , Genes Bacterianos/efectos de los fármacos , Genes Bacterianos/genética , Oxidorreductasas/genética
17.
Biochemistry ; 60(6): 465-476, 2021 02 16.
Artículo en Inglés | MEDLINE | ID: mdl-33538578

RESUMEN

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.


Asunto(s)
Arseniato Reductasas/química , Bacterias/metabolismo , Secuencia de Aminoácidos/genética , Arseniato Reductasas/metabolismo , Arseniatos/química , Arseniatos/metabolismo , Bacterias/química , Composición de Base/genética , Sitios de Unión , Catálisis , Cristalografía por Rayos X/métodos , Histidina Quinasa/metabolismo , Oxidorreductasas/metabolismo , Periplasma/metabolismo , Proteínas de Unión Periplasmáticas/química , Proteínas de Unión Periplasmáticas/metabolismo , Filogenia , ARN Ribosómico 16S/genética , Análisis de Secuencia de ADN/métodos
18.
J Basic Microbiol ; 61(4): 351-361, 2021 Apr.
Artículo en Inglés | MEDLINE | ID: mdl-33448070

RESUMEN

This study focuses on analyzing the protein expression pattern of intracellular proteins when Pseudomonas mendocina SMSKVR-3 exposed to 300 mM of arsenate to find out the proteins that are overexpressed or exclusively expressed in response to arsenate. The sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis of protein expression at different time intervals showed the highest number of protein bands (14) that are overexpressed at 8 h of the time interval. It was also observed that treatment with at least 200 mM of As(V) is required to induce a difference in protein expression. Two-dimensional (2D)-PAGE analysis of 8-h sample exhibited 146 unique spots, 45 underexpressed, and 46 overexpressed spots in arsenate-treated sample. Based on the highest percent volume and fold change, three unique spots and one overexpressed spot were selected and analyzed by matrix-assisted laser desorption/ionization-time of flight (MALDI-TOF/TOF) mass spectrometry (MS) analysis followed by the MASCOT search. These proteins were identified as ribosome-recycling factor (20.13 kDa), polyphosphate:ADP/GDP phosphotransferase (40.88 kDa), ribonuclease P protein component (14.96 kDa) and cobalt-precorrin-5B C(1)-methyltransferase (38.43 kDa) with MASCOT score of 54, 81, 94, and 100, respectively. All of these proteins help the bacteria to overcome arsenate stress.


Asunto(s)
Arseniatos/metabolismo , Arseniatos/toxicidad , Pseudomonas mendocina/efectos de los fármacos , Pseudomonas mendocina/metabolismo , Proteínas Bacterianas/metabolismo , Electroforesis en Gel Bidimensional , Electroforesis en Gel de Poliacrilamida , Espectrometría de Masa por Láser de Matriz Asistida de Ionización Desorción
19.
Int J Mol Sci ; 22(3)2021 Jan 23.
Artículo en Inglés | MEDLINE | ID: mdl-33498785

RESUMEN

: Phosphorous, in the form of phosphate, is a key element in the nutrition of all living beings. In nature, it is present in the form of phosphate salts, organophosphates, and phosphonates. Bacteria transport inorganic phosphate by the high affinity phosphate transport system PstSCAB, and the low affinity PitH transporters. The PstSCAB system consists of four components. PstS is the phosphate binding protein and discriminates between arsenate and phosphate. In the Streptomyces species, the PstS protein, attached to the outer side of the cell membrane, is glycosylated and released as a soluble protein that lacks its phosphate binding ability. Transport of phosphate by the PstSCAB system is drastically regulated by the inorganic phosphate concentration and mediated by binding of phosphorylated PhoP to the promoter of the PstSCAB operon. In Mycobacterium smegmatis, an additional high affinity transport system, PhnCDE, is also under PhoP regulation. Additionally, Streptomyces have a duplicated low affinity phosphate transport system encoded by the pitH1-pitH2 genes. In this system phosphate is transported as a metal-phosphate complex in simport with protons. Expression of pitH2, but not that of pitH1 in Streptomyces coelicolor, is regulated by PhoP. Interestingly, in many Streptomyces species, three gene clusters pitH1-pstSCAB-ppk (for a polyphosphate kinase), are linked in a supercluster formed by nine genes related to phosphate metabolism. Glycerol-3-phosphate may be transported by the actinobacteria Corynebacterium glutamicum that contains a ugp gene cluster for glycerol-3-P uptake, but the ugp cluster is not present in Streptomyces genomes. Sugar phosphates and nucleotides are used as phosphate source by the Streptomyces species, but there is no evidence of the uhp gene involved in the transport of sugar phosphates. Sugar phosphates and nucleotides are dephosphorylated by extracellular phosphatases and nucleotidases. An isolated uhpT gene for a hexose phosphate antiporter is present in several pathogenic corynebacteria, such as Corynebacterium diphtheriae, but not in non-pathogenic ones. Phosphonates are molecules that contains phosphate linked covalently to a carbon atom through a very stable C-P bond. Their utilization requires the phnCDE genes for phosphonates/phosphate transport and genes for degradation, including those for the subunits of the C-P lyase. Strains of the Arthrobacter and Streptomyces genera were reported to degrade simple phosphonates, but bioinformatic analysis reveals that whole sets of genes for putative phosphonate degradation are present only in three Arthrobacter species and a few Streptomyces species. Genes encoding the C-P lyase subunits occur in several Streptomyces species associated with plant roots or with mangroves, but not in the laboratory model Streptomyces species; however, the phnCDE genes that encode phosphonates/phosphate transport systems are frequent in Streptomyces species, suggesting that these genes, in the absence of C-P lyase genes, might be used as surrogate phosphate transporters. In summary, Streptomyces and related actinobacteria seem to be less versatile in phosphate transport systems than Enterobacteria.


Asunto(s)
Actinobacteria/metabolismo , Proteínas Bacterianas/metabolismo , Monoéster Fosfórico Hidrolasas/metabolismo , Actinobacteria/genética , Arseniatos/metabolismo , Proteínas Bacterianas/genética , Transporte Biológico , Regulación Bacteriana de la Expresión Génica , Glicosilación , Organofosfonatos/metabolismo , Proteínas de Transporte de Fosfato/genética , Proteínas de Transporte de Fosfato/metabolismo , Fosfatos/metabolismo , Regiones Promotoras Genéticas , Transducción de Señal , Streptomyces/genética , Streptomyces/metabolismo , Ácidos Teicoicos/metabolismo
20.
FEMS Microbiol Ecol ; 97(3)2021 03 08.
Artículo en Inglés | MEDLINE | ID: mdl-33512483

RESUMEN

Terribacillus sp. AE2B 122 is an environmental strain isolated from olive-oil agroindustry wastes. This strain displays resistance to arsenic, one of the most ubiquitous carcinogens found in nature. Terribacillus sp. AE2B 122 possesses an unusual ars operon, consisting of the transcriptional regulator (arsR) and arsenite efflux pump (arsB) but no adjacent arsenate reductase (arsC) locus. Expression of arsR and arsB was induced when Terribacillus was exposed to sub-lethal concentrations of arsenate. Heterologous expression of the arsB homologue in Escherichia coli∆arsRBC demonstrated that it conferred resistance to arsenite and reduced the accumulation of arsenic inside the cells. Two members of the arsC-like family (Te3384 and Te2854) found in the Terribacillus genome were not induced by arsenic, but their heterologous expression in E. coli ∆arsC and ∆arsRBC increased the accumulation of arsenic in both strains. We found that both Te3384 and Te2854 slightly increased resistance to arsenate in E. coli ∆arsC and ∆arsRBC, possibly by chelation of arsenic or by increasing the resistance to oxidative stress. Finally, arsenic speciation assays suggest that Terribacillus is incapable of arsenate reduction, in agreement with the lack of an arsC homologue in the genome.


Asunto(s)
Arsénico , Arsenitos , Arseniatos/metabolismo , Arseniatos/toxicidad , Arsénico/metabolismo , ATPasas Transportadoras de Arsenitos , Arsenitos/metabolismo , Proteínas Bacterianas/genética , Proteínas Bacterianas/metabolismo , Escherichia coli/genética , Escherichia coli/metabolismo , Bombas Iónicas/genética , Complejos Multienzimáticos/genética , Operón
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