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Related Concept Videos

Microbes and the Sulfur Cycle01:29

Microbes and the Sulfur Cycle

Sulfur is a vital element in Earth's biogeochemical systems. It transitions through various inorganic states, including sulfate (SO₄²⁻), elemental sulfur (S⁰), and sulfide (S²⁻). Abiotic and biological mechanisms across oxic and anoxic environments intricately mediate these transformations. Sulfate, the most oxidized form of sulfur, is predominantly stored in rocks, marine sediments, and oceanic waters, acting as a long-term reservoir in the global sulfur cycle.In oxic environments,...
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Sulfur Assimilation

Sulfur is an essential element in biological systems, contributing to synthesizing key biomolecules, including amino acids such as cysteine and methionine, and cofactors such as coenzyme A and biotin. Microorganisms primarily assimilate sulfur as sulfate (SO₄²⁻) from the environment, which must undergo a series of biochemical transformations before it can be incorporated into cellular components. As sulfate is highly oxidized, it must undergo assimilatory sulfate reduction to become...
Mass Spectrometry: Isotope Effect01:13

Mass Spectrometry: Isotope Effect

Most elements exist in nature as a mixture of isotopes. The isotopes differ in weight due to their respective number of neutrons. The molecular weight of a molecule is different depending on the specific isotope of its elements involved. As a result, the mass spectrum of the molecule exhibits peaks from the same fragment at multiple positions. The positions of these mass signals depend on the mass differences between isotopes. Furthermore, the intensity of these signals is dependent on the...
¹³C NMR: ¹H–¹³C Decoupling01:04

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The probability of having two carbon-13 atoms next to each other is negligible because of the low natural abundance of carbon-13. Consequently, peak splitting due to carbon-carbon spin-spin coupling is not observed in spectra. However, protons up to three sigma bonds away split the carbon signal according to the n+1 rule, resulting in complicated spectra.
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Mass Spectrometry: Molecular Fragmentation Overview01:20

Mass Spectrometry: Molecular Fragmentation Overview

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Mass Spectrometry: Alkyl Halide Fragmentation01:22

Mass Spectrometry: Alkyl Halide Fragmentation

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Related Experiment Video

Updated: May 31, 2026

Preparation of Authigenic Pyrite from Methane-bearing Sediments for In Situ Sulfur Isotope Analysis Using SIMS
09:31

Preparation of Authigenic Pyrite from Methane-bearing Sediments for In Situ Sulfur Isotope Analysis Using SIMS

Published on: August 31, 2017

Large sulfur isotope fractionation does not require disproportionation.

Min Sub Sim1, Tanja Bosak, Shuhei Ono

  • 1Department of Earth, Atmospheric, and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, MA 02139, USA. mssim@mit.edu

Science (New York, N.Y.)
|July 2, 2011
PubMed
Summary

Sulfur isotope data in rocks may not always indicate complex sulfur cycling. Marine bacteria alone can cause significant sulfur-34 depletions, challenging previous interpretations of Earth

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Combined Size and Density Fractionation of Soils for Investigations of Organo-Mineral Interactions
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Last Updated: May 31, 2026

Preparation of Authigenic Pyrite from Methane-bearing Sediments for In Situ Sulfur Isotope Analysis Using SIMS
09:31

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Published on: August 31, 2017

Separation of Uranium and Thorium for 230Th-U Dating of Submarine Hydrothermal Sulfides
08:43

Separation of Uranium and Thorium for 230Th-U Dating of Submarine Hydrothermal Sulfides

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Combined Size and Density Fractionation of Soils for Investigations of Organo-Mineral Interactions
08:38

Combined Size and Density Fractionation of Soils for Investigations of Organo-Mineral Interactions

Published on: February 15, 2019

Area of Science:

  • Geochemistry
  • Microbiology
  • Earth History

Background:

  • Sulfur isotopes in sedimentary sulfides and sulfates are key to understanding Earth's sulfur cycle.
  • Large depletions of sulfur-34 ((34)S) in sulfides relative to sulfates (exceeding 47‰) typically suggest sulfur disproportionation alongside sulfate reduction.

Purpose of the Study:

  • To investigate if sulfate-reducing bacteria alone can produce large sulfur isotope fractionations.
  • To re-evaluate the interpretation of sedimentary sulfur isotope records, particularly concerning early Earth environments.

Main Methods:

  • Culturing a marine sulfate-reducing bacterium under controlled laboratory conditions.
  • Measuring sulfur isotope compositions ((34)S) in both sulfate and sulfide produced by the bacteria.

Main Results:

  • A pure culture of marine sulfate-reducing bacteria achieved significant sulfur-34 depletions of up to 66‰.
  • This fractionation occurred solely through sulfate reduction, without extracellular sulfur oxidation or disproportionation.

Conclusions:

  • Large sulfur isotope fractionations in ancient sedimentary rocks do not exclusively indicate sulfur disproportionation or complex sulfur cycling.
  • The findings challenge the use of such fractionations as unambiguous proxies for the Proterozoic oxygenation events or specific metabolisms.