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Micron-scale mapping of sulfur cycling across the oxycline of a cyanobacterial mat: a paired nanoSIMS and CARD-FISH approach

Fike, David Andrew and Gammon, Crystal Lynn and Ziebis, Wiebke and Orphan, Victoria Jeanne (2008) Micron-scale mapping of sulfur cycling across the oxycline of a cyanobacterial mat: a paired nanoSIMS and CARD-FISH approach. ISME Journal, 2 (7). pp. 749-759. ISSN 1751-7362. doi:10.1038/ismej.2008.39.

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The metabolic activities of microbial mats have likely regulated biogeochemical cycling over most of Earth's history. However, the relationship between metabolic activity and the establishment of isotopic geochemical gradients in these mats remains poorly constrained. Here we present a parallel microgeochemical and microbiological study of micron-scale sulfur cycling within hypersaline microbial mats from Guerrero Negro, Baja California Sur, Mexico. Dissolved sulfide within the mats was captured on silver discs and analyzed for its abundance and δ^(34)S isotopic composition using high-resolution secondary ion mass spectrometry (nanoSIMS). These results were compared to sulfide and oxygen microelectrode profiles. Two-dimensional microgeochemical mapping revealed well-defined laminations in sulfide concentration (on scales from 1 to 200 μm), trending toward increased sulfide concentrations at depth. Sulfide δ^(34)S decreased from ~+10‰ to −20‰ in the uppermost 3 mm and oscillated repeatedly between −10‰ and −30‰ down to a depth of 8 mm. These variations are attributed to spatially variable bacterial sulfate reduction within the mat. A parallel examination of the spatial distribution of known sulfate-reducing bacteria within the family Desulfobacteraceae was conducted using catalyzed reporter deposition fluorescence in situ hybridization. Significant concentrations of Desulfobacteraceae were observed in both oxic and anoxic zones of the mat and occurred in several distinct layers, in large aggregates and heterogeneously dispersed as single cells throughout. The spatial distribution of these microorganisms is consistent with the variation in sulfide concentration and isotopic composition we observed. The parallel application of the methodologies developed here can shed light on micron-scale sulfur cycling within microbially dominated sedimentary environments.

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Fike, David Andrew0000-0003-2848-0328
Orphan, Victoria Jeanne0000-0002-5374-6178
Additional Information:© 2008 International Society for Microbial Ecology. Received 10 January 2008; revised 17 March 2008; accepted 18 March 2008; published online 5 June 2008. We would like to acknowledge the Gordon and Betty Moore Foundation and the Caltech Center for Geochemical and Cosmochemical Microanalysis for funding (to VJO) as well as support from National Aeronautics and Space Administration Grant NAI02-003-0001 issued through the Astrobiology Program. DAF was supported by the Caltech OK Earl Postdoctoral Fellowship. CLG was supported by a National Science Foundation Graduate Research Fellowship. We would like to thank Yunbin Guan, John Eiler and Tina Treude for analytical assistance and invaluable discussions, Bill Ussler for discussions and assistance with methodological development, Frank Stadermann for discussions and Dirk de Beer for a critical reading of this manuscript. We are also indebted to the NASA Ames group (Tori Hoehler, Niko Finke, Kendra Turk, Mike Kubo, Linda Jahnke and David DesMarais) for support and assistance with sample collections.
Funding AgencyGrant Number
Gordon and Betty Moore FoundationUNSPECIFIED
Caltech Center for Geochemical and Cosmochemical MicroanalysisUNSPECIFIED
Caltech O. K. Earl Postdoctoral FellowshipUNSPECIFIED
NSF Graduate Research FellowshipUNSPECIFIED
Subject Keywords:Guerrero Negro; in situ hybridization; Microcoleus; nanoSIMS; sulfate-reducing bacteria; sulfur isotopes
Issue or Number:7
Record Number:CaltechAUTHORS:20130510-110748396
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:38423
Deposited On:13 May 2013 14:38
Last Modified:09 Nov 2021 23:37

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