Arsenic （As） is a pervasive and ubiquitous environmental toxin that has created catastrophic human health problems world-wide. Chlamydomonas reinhardtii is a unicellular green alga, which exists ubiquitously in fres...Arsenic （As） is a pervasive and ubiquitous environmental toxin that has created catastrophic human health problems world-wide. Chlamydomonas reinhardtii is a unicellular green alga, which exists ubiquitously in freshwater aquatic systems. Arsenic metabolism processes of this alga through arsenate reduction and sequent store and efflux were investigated. When supplied with 10 μmol/L arsenate, arsenic speciation analysis showed that arsenite concentration increased from 5.7 to 15.7 mg/kg dry weight during a 7-day period, accounting for 18%–24% of the total As in alga. When treated with different levels of arsenate （10, 20, 30, 40, 50 μmol/L） for 7 days, the arsenite concentration increased with increasing external arsenate concentrations, the proportion of arsenite was up to 23%–28% of the total As in alga. In efflux experiments, both arsenate and arsenite could be found in the efflux solutions. Additionally, the efflux of arsenate was more than that of arsenite. Furthermore, two arsenate reductase genes of C. reinhardtii （CrACR2s） were cloned and expressed in Escherichia coli strain WC3110 （？arsC） for the first time. The abilities of both CrACR2s genes to complement the arsenate- sensitive strain were examined. CrACR2.1 restored arsenate resistance at 0.8 mmol/L. However, CrACR2.2 showed much less ability to complement. The gene products were demonstrated to reduce arsenate to arsenite in vivo. In agreement with the complementation results, CrACR2.1 showed higher reduction ability than CrACR2.2, when treated with 0.4 mmol/L arsenate for 16 hr incubation.展开更多
Many investigations suggest that dissimilatory arsenate-respiring prokaryotes (DARPs) play a key role in stimulating reductive mobilization of As from solid phase into groundwater,but it is not clear how environmental...Many investigations suggest that dissimilatory arsenate-respiring prokaryotes (DARPs) play a key role in stimulating reductive mobilization of As from solid phase into groundwater,but it is not clear how environmental Mn(Ⅱ) affects the DARPs-mediated reductive mobilization of arsenic.To resolve this issue,we collected soil samples from a realgar tailingsaffected area.We found that there were diverse arsenate-respiratory reductase (arr) genes in the soils.The microbial communities had high arsenate-respiring activity,and were able to efficiently stimulate the reductive mobilization of As.Compared to the microcosms without Mn(Ⅱ),addition of 10 mmol/L Mn(Ⅱ) to the microcosms led to 23.99%-251.79% increases in the microbial mobilization of As,and led to 133.3%-239.2% increases in the abundances of arr genes.We further isolated a new cultivable DARP,Bacillus sp.F11,from the arseniccontaminated soils.It completely reduced 1 mmol/L As(V) in 5 days under the optimal reaction conditions.We further found that it was able to efficiently catalyze the reductive mobilization and release of As from the solid phase;the addition of 2 mmol/L Mn(Ⅱ) led to 98.49%-248.78% increases in the F11 cells-mediated reductive mobilization of As,and70.6%-104.4% increases in the arr gene abundances.These data suggest that environmental Mn(Ⅱ) markedly increased the DARPs-mediated reductive mobilization of As in arseniccontaminated soils.This work provided a new insight into the close association between the biogeochemical cycles of arsenic and manganese.展开更多
Arsenic is a ubiquitous environmental pollutant.Microbe-mediated arsenic biotransformations significantly infuence arsenic mobility and toxicity.Arsenic transformations by soil and aquatic organisms have been well doc...Arsenic is a ubiquitous environmental pollutant.Microbe-mediated arsenic biotransformations significantly infuence arsenic mobility and toxicity.Arsenic transformations by soil and aquatic organisms have been well documented,while little is known regarding effects due to endophytic bacteria.An endophyte Pseudomonas putida ARS1 was isolated from rice grown in arsenic contaminated soil.P.putida ARS1 shows high tolerance to arsenite(As(Ⅲ))and arsenate(As(V)),and exhibits efficient As(V)reduction and As(Ⅲ)effux activities.When exposed to 0.6 mg/L As(V),As(V)in the medium was completely converted to As(Ⅲ)by P.putida ARS1 within 4 hr.Genome sequencing showed that P.putida ARS1 has two chromosomal arsenic resistance gene clusters(arsRCBH)that contribute to efficient As(V)reduction and As(Ⅲ)effux,and result in high resistance to arsenicals.Wolffia globosa is a strong arsenic accumulator with high potential for arsenic phytoremediation,which takes up As(Ⅲ)more efficiently than As(V).Co-culture of P.putida ARS1 and W.globosa enhanced arsenic accumulation in W.globosa by 69%,and resulted in 91%removal of arsenic(at initial concentration of 0.6 mg/L As(V))from water within 3 days.This study provides a promising strategy for in situ arsenic phytoremediation through the cooperation of plant and endophytic bacterium.展开更多
A mesophilic,Gram-negative,arsenite[As（Ⅲ）]-oxidizing and arsenate[As（V）]-reducing bacterial strain,Pseudomonas sp.HN-2,was isolated from an As-contaminated soil.Phylogenetic analysis based on 16 S r RNA gene sequ...A mesophilic,Gram-negative,arsenite[As（Ⅲ）]-oxidizing and arsenate[As（V）]-reducing bacterial strain,Pseudomonas sp.HN-2,was isolated from an As-contaminated soil.Phylogenetic analysis based on 16 S r RNA gene sequencing indicated that the strain was closely related to Pseudomonas stutzeri.Under aerobic conditions,this strain oxidized 92.0%（61.4 μmol/L） of arsenite to arsenate within 3 hr of incubation.Reduction of As（V） to As（Ⅲ） occurred in anoxic conditions.Pseudomonas sp.HN-2 is among the first soil bacteria shown to be capable of both aerobic As（Ⅲ） oxidation and anoxic As（V） reduction.The strain,as an efficient As（Ⅲ） oxidizer and As（V） reducer in Pseudomonas,has the potential to impact arsenic mobility in both anoxic and aerobic environments,and has potential application in As remediation processes.展开更多
This study investigates biogeochemical reductive release of arsenate from beudantite into solution in a crater area in northern Taiwan,using a combination of X-ray absorption near-edge structure （XANES） and atomic a...This study investigates biogeochemical reductive release of arsenate from beudantite into solution in a crater area in northern Taiwan,using a combination of X-ray absorption near-edge structure （XANES） and atomic absorption spectrometry.Total arsenic （As） concentrations in the soil were more than 200 mg/kg.Over four months of laboratory experiments,less than 0.8% As was released into solution after reduction experiments.The 71% to 83% As was chemically reduced into arsenite （As（III）） and partially weathering into the soluble phase.The kinetic dissolution and re-precipitation of As,Fe,Pb and sulfate in this area of paddy soils merits further study.展开更多
High pure tellurium was prepared from raw tellurium containing copper and selenium by chemical method containing oxidation with concentrated nitric acid, leaching with hydrochloric acid, reducing with sulfur dioxide a...High pure tellurium was prepared from raw tellurium containing copper and selenium by chemical method containing oxidation with concentrated nitric acid, leaching with hydrochloric acid, reducing with sulfur dioxide and treating in hydrogen atmosphere at high temperature. Removal ratio of Cu in raw tellurium reaches 99% after raw tellurium is oxidized and leached with HNO3（69%） under the following conditions： 0.96 times stoichiometric quantity of concentrated nitric acid, 4：1 of ratio of liquid to solid, 20 °C of reaction temperature and 30 min of reaction time. Leaching ratio of Te reaches 99% after Te is leached with hydrochloric acid under the following conditions： 1.67 times stoichiometric quantity of hydrochloric acid, 4：1 of ratio of liquid to solid, 20 °C of reaction temperature and 30 min of reaction time. Tellurium powder（99.95%） is obtained when Te（IV） in leachate is reduced with sulfur dioxide. The purity of tellurium increases from 99.954% to 99.999 6% after tellurium（99.95%） is treated in hydrogen atmosphere at 723.15 K for 30 min.展开更多
基金supported by the National Natural Sci- ence Foundation of China (No. 40973058, 21077100)the Doctor Foundation of Shandong Province (No. BS2009HZ024)
文摘Arsenic （As） is a pervasive and ubiquitous environmental toxin that has created catastrophic human health problems world-wide. Chlamydomonas reinhardtii is a unicellular green alga, which exists ubiquitously in freshwater aquatic systems. Arsenic metabolism processes of this alga through arsenate reduction and sequent store and efflux were investigated. When supplied with 10 μmol/L arsenate, arsenic speciation analysis showed that arsenite concentration increased from 5.7 to 15.7 mg/kg dry weight during a 7-day period, accounting for 18%–24% of the total As in alga. When treated with different levels of arsenate （10, 20, 30, 40, 50 μmol/L） for 7 days, the arsenite concentration increased with increasing external arsenate concentrations, the proportion of arsenite was up to 23%–28% of the total As in alga. In efflux experiments, both arsenate and arsenite could be found in the efflux solutions. Additionally, the efflux of arsenate was more than that of arsenite. Furthermore, two arsenate reductase genes of C. reinhardtii （CrACR2s） were cloned and expressed in Escherichia coli strain WC3110 （？arsC） for the first time. The abilities of both CrACR2s genes to complement the arsenate- sensitive strain were examined. CrACR2.1 restored arsenate resistance at 0.8 mmol/L. However, CrACR2.2 showed much less ability to complement. The gene products were demonstrated to reduce arsenate to arsenite in vivo. In agreement with the complementation results, CrACR2.1 showed higher reduction ability than CrACR2.2, when treated with 0.4 mmol/L arsenate for 16 hr incubation.
基金supported by the General Programs (No. 41472219)the Foundations for Innovative Research Groups (No. 41521001) from the National Natural Science Foundation of China。
文摘Many investigations suggest that dissimilatory arsenate-respiring prokaryotes (DARPs) play a key role in stimulating reductive mobilization of As from solid phase into groundwater,but it is not clear how environmental Mn(Ⅱ) affects the DARPs-mediated reductive mobilization of arsenic.To resolve this issue,we collected soil samples from a realgar tailingsaffected area.We found that there were diverse arsenate-respiratory reductase (arr) genes in the soils.The microbial communities had high arsenate-respiring activity,and were able to efficiently stimulate the reductive mobilization of As.Compared to the microcosms without Mn(Ⅱ),addition of 10 mmol/L Mn(Ⅱ) to the microcosms led to 23.99%-251.79% increases in the microbial mobilization of As,and led to 133.3%-239.2% increases in the abundances of arr genes.We further isolated a new cultivable DARP,Bacillus sp.F11,from the arseniccontaminated soils.It completely reduced 1 mmol/L As(V) in 5 days under the optimal reaction conditions.We further found that it was able to efficiently catalyze the reductive mobilization and release of As from the solid phase;the addition of 2 mmol/L Mn(Ⅱ) led to 98.49%-248.78% increases in the F11 cells-mediated reductive mobilization of As,and70.6%-104.4% increases in the arr gene abundances.These data suggest that environmental Mn(Ⅱ) markedly increased the DARPs-mediated reductive mobilization of As in arseniccontaminated soils.This work provided a new insight into the close association between the biogeochemical cycles of arsenic and manganese.
基金supported by the National Natural Science Foundation of China (Nos.41991332,41977323 and 42090063)the National Institutes of Health (No.R35 GM136211)。
文摘Arsenic is a ubiquitous environmental pollutant.Microbe-mediated arsenic biotransformations significantly infuence arsenic mobility and toxicity.Arsenic transformations by soil and aquatic organisms have been well documented,while little is known regarding effects due to endophytic bacteria.An endophyte Pseudomonas putida ARS1 was isolated from rice grown in arsenic contaminated soil.P.putida ARS1 shows high tolerance to arsenite(As(Ⅲ))and arsenate(As(V)),and exhibits efficient As(V)reduction and As(Ⅲ)effux activities.When exposed to 0.6 mg/L As(V),As(V)in the medium was completely converted to As(Ⅲ)by P.putida ARS1 within 4 hr.Genome sequencing showed that P.putida ARS1 has two chromosomal arsenic resistance gene clusters(arsRCBH)that contribute to efficient As(V)reduction and As(Ⅲ)effux,and result in high resistance to arsenicals.Wolffia globosa is a strong arsenic accumulator with high potential for arsenic phytoremediation,which takes up As(Ⅲ)more efficiently than As(V).Co-culture of P.putida ARS1 and W.globosa enhanced arsenic accumulation in W.globosa by 69%,and resulted in 91%removal of arsenic(at initial concentration of 0.6 mg/L As(V))from water within 3 days.This study provides a promising strategy for in situ arsenic phytoremediation through the cooperation of plant and endophytic bacterium.
基金supported by the National Natural Science Foundation of China (No.41571451)the Special Funds for Science and Education Fusion of University of Chinese Academy of Sciences
文摘A mesophilic,Gram-negative,arsenite[As（Ⅲ）]-oxidizing and arsenate[As（V）]-reducing bacterial strain,Pseudomonas sp.HN-2,was isolated from an As-contaminated soil.Phylogenetic analysis based on 16 S r RNA gene sequencing indicated that the strain was closely related to Pseudomonas stutzeri.Under aerobic conditions,this strain oxidized 92.0%（61.4 μmol/L） of arsenite to arsenate within 3 hr of incubation.Reduction of As（V） to As（Ⅲ） occurred in anoxic conditions.Pseudomonas sp.HN-2 is among the first soil bacteria shown to be capable of both aerobic As（Ⅲ） oxidation and anoxic As（V） reduction.The strain,as an efficient As（Ⅲ） oxidizer and As（V） reducer in Pseudomonas,has the potential to impact arsenic mobility in both anoxic and aerobic environments,and has potential application in As remediation processes.
基金supported by the "National" Science Council,Taiwan(No.NSC100-2313-B002-007)
文摘This study investigates biogeochemical reductive release of arsenate from beudantite into solution in a crater area in northern Taiwan,using a combination of X-ray absorption near-edge structure （XANES） and atomic absorption spectrometry.Total arsenic （As） concentrations in the soil were more than 200 mg/kg.Over four months of laboratory experiments,less than 0.8% As was released into solution after reduction experiments.The 71% to 83% As was chemically reduced into arsenite （As（III）） and partially weathering into the soluble phase.The kinetic dissolution and re-precipitation of As,Fe,Pb and sulfate in this area of paddy soils merits further study.
文摘High pure tellurium was prepared from raw tellurium containing copper and selenium by chemical method containing oxidation with concentrated nitric acid, leaching with hydrochloric acid, reducing with sulfur dioxide and treating in hydrogen atmosphere at high temperature. Removal ratio of Cu in raw tellurium reaches 99% after raw tellurium is oxidized and leached with HNO3（69%） under the following conditions： 0.96 times stoichiometric quantity of concentrated nitric acid, 4：1 of ratio of liquid to solid, 20 °C of reaction temperature and 30 min of reaction time. Leaching ratio of Te reaches 99% after Te is leached with hydrochloric acid under the following conditions： 1.67 times stoichiometric quantity of hydrochloric acid, 4：1 of ratio of liquid to solid, 20 °C of reaction temperature and 30 min of reaction time. Tellurium powder（99.95%） is obtained when Te（IV） in leachate is reduced with sulfur dioxide. The purity of tellurium increases from 99.954% to 99.999 6% after tellurium（99.95%） is treated in hydrogen atmosphere at 723.15 K for 30 min.
