Isotope effects associated with the anaerobic oxidation of sulfite and thiosulfate by the photosynthetic bacterium, Chromatium vinosum |
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Authors: | Brian Fry Howard Gest J.M. Hayes |
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Affiliation: | Photosynthetic Bacteria Group, Department of Biology, Indiana University, Bloomington, IN 47405, U.S.A.;Biogeochemical Laboratories, Departments of Chemistry and of Geology, Indiana University, Bloomington, IN 47405, U.S.A. |
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Abstract: | Abstract The purple photosynthetic bacterium Chromatium vinosum , strain D, catalyzes several oxidations of reduced sulfur compounds under anaerobic conditions in the light: e.g., sulfide → sulfur → sulfate, sulfite → sulfate, and thiosulfate → sulfur + sulfate. Here it is shown that no sulfur isotope effect is associated with the last of these processes; isotopic compositions of the sulfur and sulfate produced can differ, however, if the sulfane and sulfonate positions within the thiosulfate have different isotopic compositions. In the second process, an observed change from an inverse to a normal isotope effect during oxidation of sulfite may indicate the operation of 2 enzymatic pathways. In contrast to heterotrophic anaerobic reduction of oxidized sulfur compounds, anaerobic oxidations of inorganic sulfur compounds by photosynthetic bacteria are characterized by relatively small isotope effects. |
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Keywords: | Stable sulfur isotopes sulfur metabolism isotope fractionation |
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