Aeromonas caviae

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Masaaki Iwanaga - One of the best experts on this subject based on the ideXlab platform.

Claudia Toma - One of the best experts on this subject based on the ideXlab platform.

Claudio C. Vásquez - One of the best experts on this subject based on the ideXlab platform.

  • On the mechanism underlying tellurite reduction by Aeromonas caviae ST dihydrolipoamide dehydrogenase
    Biochimie, 2014
    Co-Authors: Felipe A. Arenas, C.a. Leal, Camilo A. Pinto, Mauricio Arenas-salinas, W.a. Morales, Fabián A. Cornejo, Waldo A. Díaz-vásquez, Claudio C. Vásquez
    Abstract:

    Abstract The dihydrolipoamide dehydrogenase (LpdA) from the tellurite-resistant bacterium Aeromonas caviae ST reduces tellurite to elemental tellurium. To characterize this NADH-dependent activity, the A. caviae lpdA gene was subjected to site-directed mutagenesis and genes containing C45A, H322Y and E354K substitutions were individually transformed into Escherichia coli Δlpd. Cells expressing the modified genes exhibited decreased pyruvate dehydrogenase, dihydrolipoamide dehydrogenase and TR activity regarding that observed with the wild type A. caviae lpdA gene. In addition, cells expressing the altered lpdA genes showed increased oxidative stress levels and tellurite sensitivity than those carrying the wild type counterpart. The involvement of Cys residues in LpdA's TR activity was analyzed using specific inhibitors that interact with catalytic cysteines and/or disulfide bridges such as aurothiomalate, zinc or nickel. TR activity of purified LpdA was drastically affected by these compounds. Since LpdA belongs to the flavoprotein family, the involvement of the FAD/NAD(P)+-binding domain in TR activity was determined. FAD removal from purified LpdA results in loss of TR activity, which was restored with exogenously added FAD. Substitutions in E354, involved in FAD/NADH binding, resulted in low TR activity because of flavin loss. Finally, changing H322 (involved in NAD+/NADH binding) by tyrosine also resulted in altered TR activity.

  • Expression of Aeromonas caviae ST pyruvate dehydrogenase complex components mediate tellurite resistance in Escherichia coli.
    Biochemical and biophysical research communications, 2009
    Co-Authors: Miguel E. Castro, Roberto C Molina, Waldo A Diaz, Gonzalo A. Pradenas, Claudio C. Vásquez
    Abstract:

    Potassium tellurite (K{sub 2}TeO{sub 3}) is harmful to most organisms and specific mechanisms explaining its toxicity are not well known to date. We previously reported that the lpdA gene product of the tellurite-resistant environmental isolate Aeromonas caviae ST is involved in the reduction of tellurite to elemental tellurium. In this work, we show that expression of A. caviae ST aceE, aceF, and lpdA genes, encoding pyruvate dehydrogenase, dihydrolipoamide transacetylase, and dihydrolipoamide dehydrogenase, respectively, results in tellurite resistance and decreased levels of tellurite-induced superoxide in Escherichia coli. In addition to oxidative damage resulting from tellurite exposure, a metabolic disorder would be simultaneously established in which the pyruvate dehydrogenase complex would represent an intracellular tellurite target. These results allow us to widen our vision regarding the molecular mechanisms involved in bacterial tellurite resistance by correlating tellurite toxicity and key enzymes of aerobic metabolism.

  • the dihydrolipoamide dehydrogenase of Aeromonas caviae st exhibits nadh dependent tellurite reductase activity
    Biochemical and Biophysical Research Communications, 2008
    Co-Authors: Miguel E. Castro, Roberto C Molina, Waldo A Diaz, Sergio Pichuantes, Claudio C. Vásquez
    Abstract:

    Abstract Potassium tellurite (K2TeO3) is extremely toxic for most forms of life and only a limited number of organisms are naturally resistant to the toxic effects of this compound. Crude extracts prepared from the environmental isolate Aeromonas caviae ST catalize the in vitro reduction of TeO 3 2 - in a NADH-dependent reaction. Upon fractionation by ionic exchange column chromatography three major polypeptides identified as the E1, E2, and E3 components of the pyruvate dehydrogenase (PDH) complex were identified in fractions exhibiting tellurite-reducing activity. Tellurite reductase and pyruvate dehydrogenase activities co-eluted from a Sephadex gel filtration column. To determine which component(s) of the PDH complex has tellurite reductase activity, the A. caviae ST structural genes encoding for E1 (aceE), E2 (aceF), and E3 (lpdA) were independently cloned and expressed in Escherichia coli and their gene products purified. Results indicated that tellurite reductase activity lies almost exclusively in the E3 component, dihydrolipoamide dehydrogenase. The E3 component of the PDH complex from E. coli, Zymomonas mobilis, Streptococcus pneumoniae, and Geobacillus stearothermophilus also showed NADH-dependent tellurite reductase in vitro suggesting that this enzymatic activity is widely distributed among microorganisms.

Kostas A. Matis - One of the best experts on this subject based on the ideXlab platform.

  • Cadmium(II) Biosorption by Aeromonas caviae: Kinetic Modeling
    Separation Science and Technology, 2005
    Co-Authors: M. X. Loukidou, Thodoris D. Karapantsios, Anastasios I. Zouboulis, Kostas A. Matis
    Abstract:

    Abstract Biosorption of cadmium from aqueous solutions on Aeromonas caviae particles was investigated in a well‐stirred batch reactor. Equilibrium and kinetic experiments were performed at various initial bulk concentrations, biomass loads, temperatures, and ionic background. Equilibrium data were well described by typical Langmuir and Freundlich adsorption isotherms. Furthermore, a detailed analysis was conducted to test several chemical reaction kinetic models in order to identify a suitable kinetic equation, assuming that biosorption is chemical sorption controlled. Predictions based on the so‐called pseudo second order rate expression were found in satisfactory accordance with experimental data.

  • Equilibrium and kinetic modeling of chromium(VI) biosorption by Aeromonas caviae
    Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2004
    Co-Authors: M. X. Loukidou, Thodoris D. Karapantsios, Anastasios I. Zouboulis, Kostas A. Matis
    Abstract:

    Biosorption of hexavalent chromium, from aqueous solutions, on Aeromonas caviae particles was investigated in a well-stirred batch reactor. Equilibrium and kinetic experiments were performed at various initial bulk concentrations, biomass loads, temperatures and ionic background. Equilibrium data were well described by typical Langmuir and Freundlich adsorption isotherms. Furthermore, a detailed analysis has been conducted testing several chemical reaction kinetic models in order to identify a suitable kinetic equation, assuming that biosorption is chemical sorption controlled. Predictions based on the so-called pseudo second order rate expression were found in satisfactory accordance with experimental data.

  • Diffusion kinetic study of cadmium(II) biosorption by Aeromonas caviae
    Journal of Chemical Technology & Biotechnology, 2004
    Co-Authors: M. X. Loukidou, Thodoris D. Karapantsios, Anastasios I. Zouboulis, Kostas A. Matis
    Abstract:

    The removal of cadmium from aqueous solution by sorption on Aeromonas caviae particles was investigated in a well-stirred batch reactor. Equilibrium and kinetic experiments were performed at various initial bulk concentrations, biomass loads and temperatures. Biosorption equilibrium was established in about 1 h and biosorption was well described by the Langmuir and Freundlich biosorption isotherms. The maximum biosorption capacity was found as 155.32 mg Cd(II) g−1 at 20 °C. The obtained sorption capacity is appreciably high for most experimental conditions; so A caviae may be considered as a suitable biosorbent for the removal of cadmium. Moreover, the sorption rate of cadmium onto A caviae particles was particularly sensitive to initial bulk concentration and solid load. A detailed analysis was conducted, examining several diffusion (external and intraparticle) kinetic models in order to identify a suitable rate expression. The results are discussed and indicate that biosorption of cadmium is a complex process that is described more correctly by more than one model. Copyright © 2004 Society of Chemical Industry

  • Diffusion Kinetic Study of Chromium(VI) Biosorption by Aeromonas caviae
    Industrial & Engineering Chemistry Research, 2004
    Co-Authors: M. X. Loukidou, Thodoris D. Karapantsios, And Anastasios I. Zouboulis, Kostas A. Matis
    Abstract:

    The removal of chromium from aqueous solution in a well-stirred batch reactor by sorption on Aeromonas caviae biomass particles, isolated from potable groundwater supplies, was investigated. Equilibrium and kinetic experiments were performed at various initial bulk concentrations, biomass loads, and temperatures, with promising results. It was seen that the sorption capacity is appreciable for most experimental conditions, so the biomass can be considered as a suitable biosorbent for applications. Moreover, the sorption rate of the metal ions was found to be particularly sensitive to both the initial bulk concentration and the biomass load. A detailed analysis was conducted examining several diffusion (external and intraparticle) kinetic models to identify a suitable rate expression, and interesting conclusions were reached. In this effort, information from SEM analyses and certain desorption runs was also incorporated.

M. John Albert - One of the best experts on this subject based on the ideXlab platform.

  • Structural studies of the O-antigenic polysaccharide from an Aeromonas caviae strain
    Carbohydrate Research, 1996
    Co-Authors: Malin Linnerborg, Göran Widmalm, Motiur Rahman, Per-erik Jansson, Tord Holme, Firdausi Qadri, M. John Albert
    Abstract:

    The structure of the O-antigenic polysaccharide from a strain of Aeromonas caviae, isolated from the stools of a patient with diarrhoea, has been investigated. Sugar analysis, methylation analyses, and a uronic acid degradation together with NMR spectroscopy were the principal methods used. The sequence of the sugar residues could be determined by NOESY and HMBC experiments. It is concluded that the polysaccharide is composed of pentasaccharide repeating units with the following structure:

  • Structural studies of the O-antigenic polysaccharide from an Aeromonas caviae strain
    Carbohydrate research, 1996
    Co-Authors: Malin Linnerborg, Göran Widmalm, Motiur Rahman, Per-erik Jansson, Tord Holme, Firdausi Qadri, M. John Albert
    Abstract:

    The structure of the O-antigenic polysaccharide from a strain of Aeromonas caviae, isolated from the stools of a patient with diarrhoea, has been investigated. Sugar analysis, methylation analyses, and a uronic acid degradation together with NMR spectroscopy were the principal methods used. The sequence of the sugar residues could be determined by NOESY and HMBC experiments. It is concluded that the polysaccharide is composed of pentasaccharide repeating units with the following structure: [sequence: see text]