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Stefan Hörtensteiner - One of the best experts on this subject based on the ideXlab platform.

  • inhibition of bacteriochlorophyll biosynthesis in the purple phototrophic bacteria rhodospirillumrubrum and rhodobacter capsulatus grown in the presence of a Toxic Concentration of selenite
    BMC Microbiology, 2018
    Co-Authors: Janine Kessi, Stefan Hörtensteiner
    Abstract:

    Background In many works, the chemical composition of bacterially-produced elemental selenium nanoparticles (Se0-nanoparticles) was investigated using electron dispersive X-ray analysis. The results suggest that these particles should be associated with organic compounds. However, a complete analysis of their chemical composition is still missing. Aiming at identifying organic compounds associated with the Se0-nanoparticles produced by the purple phototrophic bacteria Rhodospirillum rubrum and Rhodobacter capsulatus (α group of the proteobacteria), we used MALDI-TOF spectrometry.

  • Inhibition of bacteriochlorophyll biosynthesis in the purple phototrophic bacteria Rhodospirillumrubrum and Rhodobacter capsulatus grown in the presence of a Toxic Concentration of selenite
    BMC, 2018
    Co-Authors: Janine Kessi, Stefan Hörtensteiner
    Abstract:

    Abstract Background In many works, the chemical composition of bacterially-produced elemental selenium nanoparticles (Se0-nanoparticles) was investigated using electron dispersive X-ray analysis. The results suggest that these particles should be associated with organic compounds. However, a complete analysis of their chemical composition is still missing. Aiming at identifying organic compounds associated with the Se0-nanoparticles produced by the purple phototrophic bacteria Rhodospirillum rubrum and Rhodobacter capsulatus (α group of the proteobacteria), we used MALDI-TOF spectrometry. Results This technic revealed that numerous signals obtained from particles produced by both species of bacteria were from metabolites of the photosynthetic system. Furthermore, not only bacteriochlorophyll a, bacteriopheophytin a, and bacteriopheophorbide a, which are known to accumulate in stationary phase cultures of these bacteria grown phototrophically in the absence of selenite, were identified. The particles were also associated with intermediary metabolites of the bacteriochlorophyll a biosynthesis pathway such as protoporphyrin IX, protoporphyrin IX monomethyl ester, bacteriochlorophyllide a and, most likely, Mg-protoporphyrin IX-monomethyl ester, as well as with oxidation products of the substrates of protochlorophyllide reductase and chlorin reductase. Conclusion Accumulation of intermediary metabolites of the bacteriochlorophyll biosynthesis pathway in these purple phototrophic bacteria was attributed to inhibition of oxygen-sensitive enzymes involved in this pathway. Consistent with this interpretation it has been reported that these bacteria reduce selenite intracellularly, that they contain high levels of glutathione and that the reduction of selenite with glutathione is a very fast reaction accompanied by the production of reactive oxygen species. As many enzymes involved in the biosynthesis of bacteriochlorophyll contain [Fe-S] clusters in their active site, which are known to be degraded in the presence of reactive oxygen species as well as in the presence of molecular oxygen, we concluded that the substrates of these enzymes accumulate in cells during selenite reduction. Association of metabolites of bacteriochlorophyll biosynthesis and degradation with the Se0-nanoparticles produced by Rhodospirillum rubrum and Rhodobacter capsulatus is proposed to result from coating of the nanoparticles with the intracytoplasmic membrane of these bacteria, where the photochemical apparatus is concentrated

Zijian Wang - One of the best experts on this subject based on the ideXlab platform.

  • application of anodic stripping voltammetry to predict the bioavailable Toxic Concentration of cu in natural water
    Applied Geochemistry, 2003
    Co-Authors: Shengbiao Huang, Zijian Wang
    Abstract:

    In this paper, the Concentration of labile Cu measured by differential pulse anodic stripping voltammetry with a double acidification method (DAM-DPASV) was used to predict the growth inhibition of Cu on the alga Scenedesmus oblignus (S. oblignus). The influences of alkalinity, Cl-, and different Concentrations of ethylene diamine tetraacetic acid (EDTA) and fulvic acid (FA) on the labile Concentration and Toxicity of Cu were investigated in reconstituted water and natural water. The results showed that Cl- and alkalinity did not affect labile Cu Concentration, but decreased the Toxicity of Cu to S. oblignus in the Cu Concentration range observed in fresh water. The influences of alkalinity and Cl- could be modeled if Cu-carbonate complexes and Cu-chloride complexes were considered as nonToxic species. Organic complexes of Cu with EDTA and FA did not contribute either to the labile Concentration of Cu or to the Toxicity of Cu on S. oblignus. The growth inhibition of Cu on S. oblignus in natural water could be predicted by using the bioavailable Concentration of Cu, or [Cu*], which could be calculated from the labile Cu Concentration using the DAM-DPASV method and the Concentrations of Cu-carbonate and Cu-chloride complexes obtained from the MINTEQ A2 model. (C) 2003 Elsevier Science Ltd. All rights reserved.

  • measuring the bioavailable Toxic Concentration of copper in natural water by using anodic stripping voltammetry and vibrio qinghaiensis sp nov q67 bioassay
    Chemical Speciation and Bioavailability, 2003
    Co-Authors: Shengbiao Huang, Zijian Wang
    Abstract:

    Bioassays were carried out in the culture media for Vibrio-qinghaiensis sp.Nov-Q67 and the influences of alkalinity and different Concentrations of chloride, ethylene diamine tetraacetic acid (EDTA) and natural derived fulvic acid (FA) on the labile Concentration and Toxicity of Cu were investigated. The labile Concentration of Cu was obtained by differential pulse anodic stripping voltammetry with a double acidification method (DAM-DPASV). Changes in water alkalinity and chloride Concentrations did not affect the labile Concentration of Cu, but increases of alkalinity and Concentrations of chloride reduced the Toxicity on Q67 In the presence of EDTA and FA, both labile Concentration of Cu and Toxicity were reduced. By excluding Cu-carbonate complexes and Cu-chloride from labile Concentration, a bioavailable Concentration of Cu (or [Cu*]) was obtained and used to predict the acute Toxicity of Cu on Q67. For natural waters, the labile Concentration of Cu was measured by DAM-DPASV and [Cu*] was calculated by a MINTEQ A2 software based on composition of waters. This procedure was tested for Guanting Reservoir waters by spiking different Concentration Cu. The results showed that [Cu*] was a good indicator for Cu Toxicity and could be used in field conditions.

Janine Kessi - One of the best experts on this subject based on the ideXlab platform.

  • inhibition of bacteriochlorophyll biosynthesis in the purple phototrophic bacteria rhodospirillumrubrum and rhodobacter capsulatus grown in the presence of a Toxic Concentration of selenite
    BMC Microbiology, 2018
    Co-Authors: Janine Kessi, Stefan Hörtensteiner
    Abstract:

    Background In many works, the chemical composition of bacterially-produced elemental selenium nanoparticles (Se0-nanoparticles) was investigated using electron dispersive X-ray analysis. The results suggest that these particles should be associated with organic compounds. However, a complete analysis of their chemical composition is still missing. Aiming at identifying organic compounds associated with the Se0-nanoparticles produced by the purple phototrophic bacteria Rhodospirillum rubrum and Rhodobacter capsulatus (α group of the proteobacteria), we used MALDI-TOF spectrometry.

  • Inhibition of bacteriochlorophyll biosynthesis in the purple phototrophic bacteria Rhodospirillumrubrum and Rhodobacter capsulatus grown in the presence of a Toxic Concentration of selenite
    BMC, 2018
    Co-Authors: Janine Kessi, Stefan Hörtensteiner
    Abstract:

    Abstract Background In many works, the chemical composition of bacterially-produced elemental selenium nanoparticles (Se0-nanoparticles) was investigated using electron dispersive X-ray analysis. The results suggest that these particles should be associated with organic compounds. However, a complete analysis of their chemical composition is still missing. Aiming at identifying organic compounds associated with the Se0-nanoparticles produced by the purple phototrophic bacteria Rhodospirillum rubrum and Rhodobacter capsulatus (α group of the proteobacteria), we used MALDI-TOF spectrometry. Results This technic revealed that numerous signals obtained from particles produced by both species of bacteria were from metabolites of the photosynthetic system. Furthermore, not only bacteriochlorophyll a, bacteriopheophytin a, and bacteriopheophorbide a, which are known to accumulate in stationary phase cultures of these bacteria grown phototrophically in the absence of selenite, were identified. The particles were also associated with intermediary metabolites of the bacteriochlorophyll a biosynthesis pathway such as protoporphyrin IX, protoporphyrin IX monomethyl ester, bacteriochlorophyllide a and, most likely, Mg-protoporphyrin IX-monomethyl ester, as well as with oxidation products of the substrates of protochlorophyllide reductase and chlorin reductase. Conclusion Accumulation of intermediary metabolites of the bacteriochlorophyll biosynthesis pathway in these purple phototrophic bacteria was attributed to inhibition of oxygen-sensitive enzymes involved in this pathway. Consistent with this interpretation it has been reported that these bacteria reduce selenite intracellularly, that they contain high levels of glutathione and that the reduction of selenite with glutathione is a very fast reaction accompanied by the production of reactive oxygen species. As many enzymes involved in the biosynthesis of bacteriochlorophyll contain [Fe-S] clusters in their active site, which are known to be degraded in the presence of reactive oxygen species as well as in the presence of molecular oxygen, we concluded that the substrates of these enzymes accumulate in cells during selenite reduction. Association of metabolites of bacteriochlorophyll biosynthesis and degradation with the Se0-nanoparticles produced by Rhodospirillum rubrum and Rhodobacter capsulatus is proposed to result from coating of the nanoparticles with the intracytoplasmic membrane of these bacteria, where the photochemical apparatus is concentrated

Joaquim Casal - One of the best experts on this subject based on the ideXlab platform.

  • A risk severity index for industrial plants and sites
    Journal of Hazardous Materials, 2006
    Co-Authors: Eulàlia Planas, Josep Arnaldos, B. Silvetti, Agnes Vallée, Joaquim Casal
    Abstract:

    A risk index (Risk Severity Index, S) has been devised to allow the assessment of the risk level originated by a given installation or site over the affected zone. A set of threshold levels for thermal radiation, Toxic Concentration and overpressure, together with the probabilities and frequencies associated to critical events and their effects have been the basis for calculating the values of S. A computer tool has been designed to perform a quick calculation of the diverse Risk Severity Indexes (for a critical event, for a dangerous phenomenon, for a type of effect and for the whole installation) and to plot a map of the risk severity levels around the site. The methodology has been applied to diverse test cases and it has proved to be useful for risk assessment, for comparative studies and for land use planning.

  • The assessment of risk in industrial installations : the risk severity index
    2005
    Co-Authors: Eulàlia Planas, Josep Arnaldos, B. Silvetti, Agnes Vallée, Joaquim Casal
    Abstract:

    A risk index (Risk Severity Index, S) has been devised to allow the assessment of the risk level originated by a given installation or site over the affected zone. A set of threshold levels for thermal radiation, Toxic Concentration, and overpressure, together with the probabilities and frequencies associated with critical events and their effects, have been the basis for calculating the values of S. A computer tool has been designed to perform a quick calculation of the diverse Risk Severity Indexes (for a critical event, for a dangerous phenomenon, for a type of effect and for the whole installation) and to plot a map of the risk severity levels around the site. The methodology has been applied to diverse test cases and it has proved to be useful for risk assessment, for comparative studies and for land use planning.

Shengbiao Huang - One of the best experts on this subject based on the ideXlab platform.

  • application of anodic stripping voltammetry to predict the bioavailable Toxic Concentration of cu in natural water
    Applied Geochemistry, 2003
    Co-Authors: Shengbiao Huang, Zijian Wang
    Abstract:

    In this paper, the Concentration of labile Cu measured by differential pulse anodic stripping voltammetry with a double acidification method (DAM-DPASV) was used to predict the growth inhibition of Cu on the alga Scenedesmus oblignus (S. oblignus). The influences of alkalinity, Cl-, and different Concentrations of ethylene diamine tetraacetic acid (EDTA) and fulvic acid (FA) on the labile Concentration and Toxicity of Cu were investigated in reconstituted water and natural water. The results showed that Cl- and alkalinity did not affect labile Cu Concentration, but decreased the Toxicity of Cu to S. oblignus in the Cu Concentration range observed in fresh water. The influences of alkalinity and Cl- could be modeled if Cu-carbonate complexes and Cu-chloride complexes were considered as nonToxic species. Organic complexes of Cu with EDTA and FA did not contribute either to the labile Concentration of Cu or to the Toxicity of Cu on S. oblignus. The growth inhibition of Cu on S. oblignus in natural water could be predicted by using the bioavailable Concentration of Cu, or [Cu*], which could be calculated from the labile Cu Concentration using the DAM-DPASV method and the Concentrations of Cu-carbonate and Cu-chloride complexes obtained from the MINTEQ A2 model. (C) 2003 Elsevier Science Ltd. All rights reserved.

  • measuring the bioavailable Toxic Concentration of copper in natural water by using anodic stripping voltammetry and vibrio qinghaiensis sp nov q67 bioassay
    Chemical Speciation and Bioavailability, 2003
    Co-Authors: Shengbiao Huang, Zijian Wang
    Abstract:

    Bioassays were carried out in the culture media for Vibrio-qinghaiensis sp.Nov-Q67 and the influences of alkalinity and different Concentrations of chloride, ethylene diamine tetraacetic acid (EDTA) and natural derived fulvic acid (FA) on the labile Concentration and Toxicity of Cu were investigated. The labile Concentration of Cu was obtained by differential pulse anodic stripping voltammetry with a double acidification method (DAM-DPASV). Changes in water alkalinity and chloride Concentrations did not affect the labile Concentration of Cu, but increases of alkalinity and Concentrations of chloride reduced the Toxicity on Q67 In the presence of EDTA and FA, both labile Concentration of Cu and Toxicity were reduced. By excluding Cu-carbonate complexes and Cu-chloride from labile Concentration, a bioavailable Concentration of Cu (or [Cu*]) was obtained and used to predict the acute Toxicity of Cu on Q67. For natural waters, the labile Concentration of Cu was measured by DAM-DPASV and [Cu*] was calculated by a MINTEQ A2 software based on composition of waters. This procedure was tested for Guanting Reservoir waters by spiking different Concentration Cu. The results showed that [Cu*] was a good indicator for Cu Toxicity and could be used in field conditions.