Physiology of multiple sulfur isotope fractionation during microbial sulfate reduction
type: CreativeWork
description: Microbial sulfate reduction (MSR) utilizes sulfate as an electron acceptor and produces sulfide that is depleted in heavy isotopes of sulfur relative to starting sulfate. The fractionation of S-isotopes is commonly used to trace the biogeochemical cycling of sulfur in nature, but a mechanistic understanding of factors that control the range of isotope fractionation is still lacking. This thesis investigates links between the physiology of sulfate reducing bacteria in pure cultures and multiple sulfur isotope (³², ³³, ³⁴34S, and ³⁶S) fractionation during MSR in batch and continuous culture experiments. Experiments address the influence of nutrient and electron donor conditions, including organic carbon, nitrogen, and iron, in cultures of a newly isolated marine sulfate reducing bacterium (DMSS-1). An actively growing culture of DMSS-1 produced sulfide depleted in ³⁴S by 6 to 66%o, depending on the availability and chemistry of organic electron donors. The magnitude of isotope effect correlated well with the cell specific sulfate reduction rate (csSRR), and the largest isotope effects occurred when cultures grew slowly on glucose, a recalcitrant organic substrate. These findings bridge the long-standing discrepancy between the upper limit for S-isotope effect in laboratory cultures and the corresponding observations in nature and indicate that the large (>46 %o) fractionation of S-isotopes does not unambiguously record the oxidative sulfurrecycling. When the availability of iron was limited, the increase in S-isotope fractionation was accompanied by a decrease in the cytochrome c content as well as csSRR. In contrast, growth in nitrogenlimited cultures increased both csSRR and S-isotope fractionation. The influence of individual enzymes and electron carriers involved in sulfate respiration on the fractionation of S-isotopes was also investigated in cultures of mutant strains of Desulfovibrio vulgaris Hildenborough. The mutant lacking Type I tetraheme cytochrome c₃ fra…
abstract: Microbial sulfate reduction (MSR) utilizes sulfate as an electron acceptor and produces sulfide that is depleted in heavy isotopes of sulfur relative to starting sulfate. The fractionation of S-isotopes is commonly used to trace the biogeochemical cycling of sulfur in nature, but a mechanistic understanding of factors that control the range of isotope fractionation is still lacking. This thesis investigates links between the physiology of sulfate reducing bacteria in pure cultures and multiple sulfur isotope (³², ³³, ³⁴34S, and ³⁶S) fractionation during MSR in batch and continuous culture experiments. Experiments address the influence of nutrient and electron donor conditions, including organic carbon, nitrogen, and iron, in cultures of a newly isolated marine sulfate reducing bacterium (DMSS-1). An actively growing culture of DMSS-1 produced sulfide depleted in ³⁴S by 6 to 66%o, depending on the availability and chemistry of organic electron donors. The magnitude of isotope effect correlated well with the cell specific sulfate reduction rate (csSRR), and the largest isotope effects occurred when cultures grew slowly on glucose, a recalcitrant organic substrate. These findings bridge the long-standing discrepancy between the upper limit for S-isotope effect in laboratory cultures and the corresponding observations in nature and indicate that the large (>46 %o) fractionation of S-isotopes does not unambiguously record the oxidative sulfurrecycling. When the availability of iron was limited, the increase in S-isotope fractionation was accompanied by a decrease in the cytochrome c content as well as csSRR. In contrast, growth in nitrogenlimited cultures increased both csSRR and S-isotope fractionation. The influence of individual enzymes and electron carriers involved in sulfate respiration on the fractionation of S-isotopes was also investigated in cultures of mutant strains of Desulfovibrio vulgaris Hildenborough. The mutant lacking Type I tetraheme cytochrome c₃ fra…
author: Sim, Min Sub
language: eng
keywords: Earth, Atmospheric, and Planetary Sciences.
license: http://dspace.mit.edu/handle/1721.1/7582
date published: 2012
date modified: 2026-07-22T22:20:47Z
provider: MIT
publisher: Networked Digital Library of Theses and Dissertations
type: WebPage
source organization: Massachusetts Institute of Technology

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property ID: Handle
value: http://hdl.handle.net/1721.1/77788