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Multiple sulphur isotopic interpretations of biosynthetic pathways: implications for biological signatures in the sulphur isotope record
Author(s) -
Farquhar James,
Johnston David T.,
Wing Boswell A.,
Habicht Kirsten S.,
Canfield Donald E.,
Airieau Sabine,
Thiemens Mark H.
Publication year - 2003
Publication title -
geobiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.859
H-Index - 72
eISSN - 1472-4669
pISSN - 1472-4677
DOI - 10.1046/j.1472-4669.2003.00007.x
Subject(s) - isotope , fractionation , sulfur , context (archaeology) , isotope fractionation , isotopic signature , chemistry , isotopes of sulfur , stable isotope ratio , isotope analysis , mass independent fractionation , geology , biology , paleontology , ecology , chromatography , biochemistry , physics , organic chemistry , amino acid , quantum mechanics , methionine
Isotopic fractionations produced by biosynthetic processes are the result of networks of individual biochemical reactions that operate at differing efficiencies and with distinct fractionation factors. These reaction networks determine the magnitude and direction of the net isotopic fractionation associated with a given process. Here we examine the ways that biological reaction networks control mass‐dependent isotopic fractionations of multiple sulphur isotopes. We describe how material‐flow through some networks can produce characteristic multiple‐sulphur‐isotope signatures that differ from those produced by their constituent steps and demonstrate that experimental results with Archaeaglobus fulgidus can be evaluated using multiple sulphur isotopes in the context of previously published models for dissimilatory sulphate reduction. Our evaluation of these data is consistent with the interpretation that the dependence of sulphur isotope fractionation on external sulphate concentration is rooted in differences between the forward and reverse ↔ adenosine‐5′‐phosphosulphate (APS) ↔ steps. The framework provided by our analysis has the potential to evaluate the biosynthetic pathways that produce the isotopic fractionations, to isolate the primary sources of isotopic fractionations (sulphate reduction or disproportionation reactions) and to establish criteria to identify the signature of specific sulphur metabolisms in the geological record. The results highlight the new types of information that can be obtained by including measurements of δ 33 S {δ 33 S = [( 33 S/ 32 S) sample /( 33 S/ 32 S) reference − 1]*1000} with measurements of δ 34 S.