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Insights into chemotaxonomic composition and carbon cycling of phototrophic communities in an artesian sulfur-rich spring (Zodletone, Oklahoma, USA), a possible analog for ancient microbial mat systems

Authors

  • S. I. BÜHRING,

    1. Department of Geosciences and MARUM Center for Marine Environmental Sciences, Universität Bremen, Bremen, Germany
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  • S. M. SIEVERT,

    1. Biology Department, Woods Hole Oceanographic Institution, Woods Hole, MA, USA
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  • H. M. JONKERS,

    1. Max Planck Institute for Marine Microbiology, Microsensor Group, Bremen, Germany
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    • Present address: Civil Engineering & Geosciences, Delft University of Technology, Stevinweg 1, 2628 CN Delft, The Netherlands.

  • T. ERTEFAI,

    1. Department of Geosciences and MARUM Center for Marine Environmental Sciences, Universität Bremen, Bremen, Germany
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    • Present address: WA – Organic & Isotope Geochemistry Centre, Curtin University of Technology, GPO Box U1987, Perth, WA 6845, Australia.

  • M. S. ELSHAHED,

    1. Department of Botany and Microbiology, University of Oklahoma, Norman, OK, USA
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    • Present address: WA – Organic & Isotope Geochemistry Centre, Curtin University of Technology, GPO Box U1987, Perth, WA 6845, Australia.

  • L. R. KRUMHOLZ,

    1. Department of Botany and Microbiology, University of Oklahoma, Norman, OK, USA
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  • K.-U. HINRICHS

    1. Department of Geosciences and MARUM Center for Marine Environmental Sciences, Universität Bremen, Bremen, Germany
    2. Department of Geology and Geophysics, Woods Hole Oceanographic Institution, Woods Hole, MA, USA
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  • Present address: Oklahoma State University, 1110 S. Innovation Way, Stillwater, OK 74074, USA.

Corresponding authors: Solveig I. Bühring. Tel.:+49 421 21865744; fax: +49 421 21865715; e-mail: solveig.buehring@uni-bremen.de and Stefan M. Sievert. Tel.: +1 508 2892305; fax: +1 508 4572076; e-mail: ssievert@whoi.edu

Abstract

Zodletone spring in Oklahoma is a unique environment with high concentrations of dissolved-sulfide (10 mm) and short-chain gaseous alkanes, exhibiting characteristics that are reminiscent of conditions that are thought to have existed in Earth’s history, in particular the late Archean and early-to-mid Proterozoic. Here, we present a process-oriented investigation of the microbial community in two distinct mat formations at the spring source, (1) the top of the sediment in the source pool and (2) the purple streamers attached to the side walls. We applied a combination of pigment and lipid biomarker analyses, while functional activities were investigated in terms of oxygen production (microsensor analysis) and carbon utilization (13C incorporation experiments). Pigment analysis showed cyanobacterial pigments, in addition to pigments from purple sulfur bacteria (PSB), green sulfur bacteria (GSB) and Chloroflexus-like bacteria (CLB). Analysis of intact polar lipids (IPLs) in the source sediment confirmed the presence of phototrophic organisms via diacylglycerol phospholipids and betaine lipids, whereas glyceroldialkylglyceroltetraether additionally indicated the presence of archaea. No archaeal IPLs were found in the purple streamers, which were strongly dominated by betaine lipids. 13C-bicarbonate- and -acetate-labeling experiments indicated cyanobacteria as predominant phototrophs in the source sediment, carbon was actively fixed by PSB/CLB/GSB in purple streamers by using near infrared light. Despite the presence of cyanobacteria, no oxygen could be detected in the presence of light, suggesting anoxygenic photosynthesis as the major metabolic process at this site. Our investigations furthermore indicated photoheterotrophy as an important process in both habitats. We obtained insights into a syntrophically operating phototrophic community in an ecosystem that bears resemblance to early Earth conditions, where cyanobacteria constitute an important contributor to carbon fixation despite the presence of high sulfide concentrations.

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