Sulfur isotope fractionation during bacterial reduction and disproportionation of thiosulfate and sulfite
- Max Planck Inst. for Marine Microbiology, Bremen (Germany)
- Bremen Univ. (Germany)
In bacterial cultures the authors measured sulfur isotope fractionation during transformations of thiosulfate and sulfite, pathways which may be of considerable importance in the cycling of sulfur in marine sediments and euxinic waters. They documented isotope fractionations during the reduction and disproportionation of thiosulfate and sulfite by bacterial enrichments and pure bacterial cultures from marine and freshwater environments. They also measured the isotope fractionation associated with the anoxygenic phototrophic oxidation of H{sub 2}S to thiosulfate by cyanobacteria. Except for sulfite reduction, isotope fractionations for these processes have not been previously reported. During the dissimilatory reduction of sulfite, H{sub 2}S was depleted in {sup 34}S by 6%, and during the reduction of thiosulfate to H{sub 2}S, depletions were between 7% and 11%. The largest observed isotope fractionation was associated with the bacterial disproportionation of sulfite which caused a {sup 34}S depletion in H{sub 2}S of 20--37% and a {sup 34}S enrichment in sulfate of 7--12%. During the bacterial disproportionation of thiosulfate, isotope fractionations between the outer sulfane sulfur and H{sub 2}S and between the inner sulfonate sulfur and sulfate were <4%. The authors observed isotope exchange between the two sulfur atoms of thiosulfate leading to a depletion of {sup 34}S in H{sub 2}S by up to 12% with a comparable enrichment of {sup 34}S in sulfate. No isotope fractionation was associated with the anoxygenic phototrophic oxidation of H{sub 2}S to thiosulfate. The depletion of {sup 34}S into H{sub 2}S during the bacterial reduction and disproportionation of thiosulfate and sulfite may, in addition to sulfate reduction and the bacterial disproportionation of elemental sulfur, contribute to the generation of {sup 34}S-depleted sedimentary sulfides.
- OSTI ID:
- 289457
- Journal Information:
- Geochimica et Cosmochimica Acta, Vol. 62, Issue 15; Other Information: PBD: Aug 1998
- Country of Publication:
- United States
- Language:
- English
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