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| Titel |
Microbial conversion of inorganic carbon to dimethyl sulfide in anoxic lake sediment (Plußsee, Germany) |
| VerfasserIn |
Y. S. Lin, V. B. Heuer, T. G. Ferdelman, K.-U. Hinrichs |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1726-4170
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| Digitales Dokument |
URL |
| Erschienen |
In: Biogeosciences ; 7, no. 8 ; Nr. 7, no. 8 (2010-08-16), S.2433-2444 |
| Datensatznummer |
250004931
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| Publikation (Nr.) |
 copernicus.org/bg-7-2433-2010.pdf |
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| Zusammenfassung |
| In anoxic environments, volatile methylated sulfides like methanethiol (MT)
and dimethyl sulfide (DMS) link the pools of inorganic and organic carbon
with the sulfur cycle. However, direct formation of methylated sulfides from
reduction of dissolved inorganic carbon has previously not been
demonstrated. When studying the effect of temperature on hydrogenotrophic
microbial activity, we observed formation of DMS in anoxic sediment of Lake
Plußsee at 55 °C. Subsequent experiments strongly suggested that the
formation of DMS involves fixation of bicarbonate via a reductive pathway in
analogy to methanogenesis and engages methylation of MT. DMS formation was
enhanced by addition of bicarbonate and further increased when both
bicarbonate and H2 were supplemented. Inhibition of DMS formation by
2-bromoethanesulfonate points to the involvement of methanogens. Compared to
the accumulation of DMS, MT showed the opposite trend but there was no
apparent 1:1 stoichiometric ratio between both compounds. Both DMS and MT
had negative δ13C values of −62‰ and −55‰, respectively.
Labeling with NaH13CO3 showed more rapid incorporation of
bicarbonate into DMS than into MT. The stable carbon isotopic evidence
implies that bicarbonate was fixed via a reductive pathway of
methanogenesis, and the generated methyl coenzyme M became the methyl donor
for MT methylation. Neither DMS nor MT accumulation were stimulated by
addition of the methyl-group donors methanol and syringic acid or by the
methyl-group acceptor hydrogen sulphide. The source of MT was further
investigated in a H235S labeling experiment, which demonstrated a
microbially-mediated process of hydrogen sulfide methylation to MT that
accounted for only <10% of the accumulation rates of DMS. Therefore,
the major source of the 13C-depleted MT was neither bicarbonate nor
methoxylated aromatic compounds. Other possibilities for isotopically
depleted MT, such as other organic precursors like methionine, are
discussed. This DMS-forming pathway may be relevant for anoxic environments
such as hydrothermally influenced sediments and fluids and sulfate-methane
transition zones in marine sediments. |
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