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21.
Kobayashi I Fujiwara S Saegusa H Inouhe M Matsumoto H Tsuzuki M 《Marine biotechnology (New York, N.Y.)》2006,8(1):94-101
In most photosynthetic organisms, inorganic arsenic taken up into the cells inhibits photosynthesis and cellular growth. In
a green alga, Chlamydomonas reinhardtii, 0.5 mM arsenate inhibited photosynthesis almost completely within 30 min. However, in cells acclimated with a sublethal
concentration (0.05 to 0.1 mM) of Cd, the inhibition of photosynthesis at 30 min after the addition of arsenate was relieved
by more than 50%. The concentrations of arsenic incorporated into the cells were not significantly different between the Cd-acclimated
and the non-acclimated cells. The Cd-acclimated cells accumulated Cd and synthesized phytochelatin (PC) peptides, which are
known to play an important role in detoxification of heavy metals in plants. By the addition of an inhibitor of glutathione
(an intermediate in the PC biosynthetic pathway) biosynthesis, buthionine sulfoximine, cells lost not only Cd tolerance but
also arsenate tolerance. These results suggest that glutathione and/or PCs synthesized in Cd-acclimated cells are involved
in mechanisms of arsenate tolerance.
The authors contributed equally to this work. 相似文献
22.
Zahra Souri 《Soil & Sediment Contamination》2017,26(4):457-468
The present study investigates the possible role of exogenous nitric oxide (NO) supplementation as sodium nitroprusside (SNP), on increasing phytoextraction and phytoremediation ability of arsenic hyperaccumulator, Isatis cappadocica. Arsenate (500, 1000 and 1500 µM) alone or in combination with 200 µM SNP was given to hydroponically grown plants for 14 days. The highest level of arsenate (1500 µM) reduced the plant growth and chlorophyll content, while SNP alleviated these inhibitory effects. The application of SNP significantly increased the As concentration in the root (from 1004 to 1943 mg/kg) and shoots (from 1304 to 1859 mg/kg) compared with As-stressed plants. However, SNP treatment did not affect translocation factor value significantly in the As-stressed plants which shows enhancement of both As uptake and translocation under SNP application. This is the first study demonstrating the favorable effects of SNP on As tolerance, uptake, and accumulation of highly valuable As hyperaccumulator, I. cappadocica. 相似文献
23.
Anaerobic reduction and oxidation of quinone moieties and the reduction of oxidized metals by halorespiring and related organisms 总被引:2,自引:0,他引:2
24.
A new microbial strain was isolated from an arsenic-rich terrestrial geothermal environment. The isolate, designated HR13, was identified as a Thermus species based on 16S rDNA phylogenetic relationships and close sequence similarity within the Thermus genus. Under aerobic conditions, Thermus HR13 was capable of rapidly oxidizing inorganic As(III) to As(V). As(III) was oxidized at a rate approximately 100-fold greater than abiotic rates. Metabolic energy was not gained from the oxidation reaction. In the absence of oxygen, Thermus HR13 grew by As(V) respiration coupled with lactate oxidation. The ability to oxidize and reduce arsenic has not been previously described within the Thermus genus. 相似文献
25.
Stress granules are RNP-containing particles arising in the cytoplasm in response to environmental stress. They are dynamic structures assembling and disassembling in the cytoplasm very rapidly. We have studied whether the cytoskeleton is involved in the formation of stress granules. Stress granules were induced in CV-1 cells by sodium arsenate treatment and visualized by immunofluorescent staining with antibodies either to the p170 subunit of eIF3 or to poly(A)-binding protein. Treatment with sodium arsenate for 30-120 min led to assembling of stress granules in a majority of CV-1 cells. Disruption of MT array with nocodazole treatment abolished arsenate-induced formation of stress granules. A similar effect was induced by the microtubule-depolymerizing drug vinblastine, though the influence of the microtubule-stabilizing drug paclitaxel was opposite. Nocodazole treatment did not prevent arsenate-induced phosphorylation of the eIF-2alpha factor, essential for stress granule formation, suggesting that the presence of intact MT array is required for granule assembly. Unexpectedly, treatment of cells with the actin filament-disrupting drug latrunculin B slightly enhanced stress granule formation. We propose that stress granule formation is microtubule-dependent process and likely is facilitated by the motor protein-driven movement of individual stress granule components (e.g., mRNP) along microtubules. 相似文献
26.
Microbial activity is responsible for the transformation of at least one third of the elements in the periodic table. These
transformations are the result of assimilatory, dissimilatory, or detoxification processes and form the cornerstones of many
biogeochemical cycles. Arsenic and selenium are two elements whose roles in microbial ecology have only recently been recognized.
Known as "essential toxins", they are required in trace amounts for growth and metabolism but are toxic at elevated concentrations.
Arsenic is used as an osmolite in some marine organisms while selenium is required as selenocysteine (i.e. the twenty-first
amino acid) or as a ligand to metal in some enzymes (e.g. FeNiSe hydrogenase). Arsenic resistance involves a small-molecular-weight
arsenate reductase (ArsC). The use of arsenic and selenium oxyanions for energy is widespread in prokaryotes with representative
organisms from the Crenarchaeota, thermophilic bacteria, low and high G+C gram-positive bacteria, and Proteobacteria. Recent
studies have shown that both elements are actively cycled and play a significant role in carbon mineralization in certain
environments. The occurrence of multiple mechanisms involving different enzymes for arsenic and selenium transformation indicates
several different evolutionary pathways (e.g. convergence and lateral gene transfer) and underscores the environmental significance
and selective impact in microbial evolution of these two elements.
Electronic Publication 相似文献
27.
Two sulfate-reducing bacteria, which also reduce arsenate, were isolated; both organisms oxidized lactate incompletely to
acetate. When using lactate as the electron donor, one of these organisms, Desulfomicrobium strain Ben-RB, rapidly reduced (doubling time = 8 h) 5.1 mM arsenate at the same time it reduced sulfate (9.6 mM). Sulfate
reduction was not inhibited by the presence of arsenate. Arsenate could act as the terminal electron acceptor in minimal medium
(doubling time = 9 h) in the absence of sulfate. Arsenate was reduced by a membrane-bound enzyme that is either a c-type cytochrome or is associated with such a cytochrome; benzyl-viologen-dependent arsenate reductase activity was greater
in cells grown with arsenate/sulfate than in cells grown with sulfate only. The second organism, Desulfovibrio strain Ben-RA, also grew (doubling time = 8 h) while reducing arsenate (3.1 mM) and sulfate (8.3 mM) concomitantly. No evidence
was found, however, that this organism is able to grow using arsenate as the terminal electron acceptor. Instead, it appears
that arsenate reduction by the Desulfovibrio strain Ben-RA is catalyzed by an arsenate reductase that is encoded by a chromosomally-borne gene shown to be homologous
to the arsC gene of the Escherichia coli plasmid, R773 ars system.
Received: 18 March 1999 / Accepted: 27 September 1999 相似文献
28.
Olof Hofslagare Staffan Sjöberg Göran Samuelsson 《Chemical Speciation and Bioavailability》2013,25(4):95-102
AbstractA Potentiometric titration method was used to study the adverse effect of arsenate (As(V)) and arsenite (As(III)) on inorganic carbon uptake in suspensions of the green alga Scenedesmus obliquus. The measurements were performed in a closed CO2-system with diluted synthetic seawater (1‰ salinity) as ionic medium. Usually, the algal chlorophyll concentration was 0.4 mg dm?3, while the arsenate- and arsenite-concentrations were varied within the limits 0.1 to 200 μmol dm?3. In some experiments arsenate toxicity was studied in the presence of 1 to 100 μmol dm?3 of phosphate (P(V)).With concentrations of arsenate or arsenite less than 0.1 μmol dm?3 no toxic effects were observed. However, at As-concentrations of 200 μmol dm?3, the algal carbon uptake was reduced by 41% with arsenate and 29% with arsenite, i.e., arsenate is more toxic to Scenedesmus obliquus than arsenite. The toxicity of arsenate was negligible in the presence of a ten fold excess of phosphate. This is probably due to chemical similarities between arsenate and phosphate causing competition between the ions for the binding sites.The importance of taking the speciation as well as the buffer capacity of the algal system into account, when calculating the carbon uptake, is also discussed. 相似文献
29.
Shekhar Mallick Navin Kumar Sarita Sinha Arvind Kumar Dubey Rudra Deo Tripathi Vivek Srivastav 《Physiology and Molecular Biology of Plants》2014,20(4):435-447
The study investigated the reduction in metalloid uptake at equimolar concentrations (~53.3 μM) of As(III) and As(V) in contrasting pair of rice seedlings by pretreating with H2O2 (1.0 μM) and SA (1.0 mM). Results obtained from the contrasting pair (arsenic tolerant vs. sensitive) of rice seedlings (cv. Pant Dhan 11 and MTU 7029, respectively) shows that pretreatment of H2O2 and H2O2 + SA reduces As(V) uptake significantly in both the cultivars, while no reduction in the As(III) uptake. The higher growth inhibition, higher H2O2 and TBARS content in sensitive cultivar against As(III) and As(V) treatments along with higher As accumulation (~1.2 mg g−1 dw) than in cv. P11, unravels the fundamental difference in the response between the sensitive and tolerant cultivar. In the H2O2 pretreated plants, the translocation of As increased in tolerant cultivar against AsIII, whereas, it decreased in sensitive cultivar both against AsIII and AsV. In both the cultivars translocation of Mn increased in the H2O2 pretreated plants against As(III), whereas, the translocation of Cu increased against As(V). In tolerant cultivar the translocation of Fe increased against As(V) with H2O2 pretreatment whereas, it decreased in the sensitive cultivar. In both the cultivars, Zn translocation increased against As(III) and decreased against As(V). The higher level of H2O2 and SOD (EC 1.15.1.1) activity in sensitive cultivar whereas, higher, APX (EC 1.11.1.11), GR (EC 1.6.4.2) and GST (EC 1.6.4.2) activity in tolerant cultivar, also demonstrated the differential anti-oxidative defence responses between the contrasting rice cultivars.
Electronic supplementary material
The online version of this article (doi:10.1007/s12298-014-0255-1) contains supplementary material, which is available to authorized users. 相似文献30.
Respiratory arsenate reductase as a bidirectional enzyme 总被引:1,自引:0,他引:1
Christine Richey Shelley E. Hoeft Partha Basu 《Biochemical and biophysical research communications》2009,382(2):298-302
The haloalkaliphilic bacterium Alkalilimnicola ehrlichii is capable of anaerobic chemolithoautotrophic growth by coupling the oxidation of arsenite (As(III)) to the reduction of nitrate and carbon dioxide. Analysis of its complete genome indicates that it lacks a conventional arsenite oxidase (Aox), but instead possesses two operons that each encode a putative respiratory arsenate reductase (Arr). Here we show that one homolog is expressed under chemolithoautotrophic conditions and exhibits both arsenite oxidase and arsenate reductase activity. We also demonstrate that Arr from two arsenate respiring bacteria, Alkaliphilus oremlandii and Shewanella sp. strain ANA-3, is also biochemically reversible. Thus Arr can function as a reductase or oxidase. Its physiological role in a specific organism, however, may depend on the electron potentials of the molybdenum center and [Fe-S] clusters, additional subunits, or constitution of the electron transfer chain. This versatility further underscores the ubiquity and antiquity of microbial arsenic metabolism. 相似文献