Bacterial abundance and composition in marine sediments bene

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TitleBacterial abundance and composition in marine sediments beneath the Ross Ice Shelf, AntarcticaAbstractMarine sediments of the Ross Sea, Antarctica, harbor microbial communities that play a significant role in the decomposition, mineralization, and recycling of organic carbon (OC). In this study, the cell densities within a 153-cm sediment core from the Ross Sea were estimated based on microbial phospholipid fatty acid (PLFA) concentrations and acridine orange direct cell counts. The resulting densities were as high as 1.7 xÂ— 107 cells mL-1 in the top ten centimeters of sediments. These densities are lower than those calculated for most near-shore sites but consistent with deep-sea locations with comparable sedimentation rates. The delta 13C measurements of PLFAs and sedimentary and dissolved carbon sources, in combination with ribosomal RNA (SSU rRNA) gene pyrosequencing, were used to infer microbial metabolic pathways. The delta13C values of dissolved inorganic carbon (DIC) in porewaters ranged downcore from -2.5 per mil to -3.7 per mil, while delta13C values for the corresponding sedimentary particulate OC (POC) varied from -26.2 per mil to -23.1Â€ per mil. The delta13C values of PLFAs ranged between -29 per mil and -35 per mil throughout the sediment core, consistent with a microbial community dominated by heterotrophs. The SSU rRNA gene pyrosequencing revealed that members of this microbial community were dominated by beta-, delta-, and y-Proteobacteria, Actinobacteria, Chloroflexi and Bacteroidetes. Among the sequenced organisms, many appear to be related to known heterotrophs that utilize OC sources such as amino acids, oligosaccharides, and lactose, consistent with our interpretation from delta13C PLFA analysis. Integrating phospholipids analyses with porewater chemistry, delta13CDIC and delta13CPOC values and SSU rRNA gene sequences provides a more comprehensive understanding of microbial communities and carbon cycling in marine sediments, including those of this unique ice shelf environment. Copyright 2013 John Wiley and Sons Ltd.AcknowledgementsThe authors would like to thank ANDRILL for samples and funding, especially Alex Pyne for his efforts with the push cores. We also like to thank Chuck Pepe-Ranney, Chase Williamson, and Jason Sahl for assistance in the laboratory and with bioinformatics, David Mucciarone for his help with 13C measurements, as well as Chris Mills, Andrew Glossner and Hallgerd Eydal for their editorial comments. We thank our four anonymous reviewers for their thoughtful and very constructive reviews and the editorial handling of Anne Louise Reysenbach and Kurt Konhauser.

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1st AuthorCarr, S.AuthorCarr, S.Vogel, S.Dunbar, R.Brandes, J.Spear, J.Levy, R.Naish, T.Powell, R.Wakeham, S.Mandernack, K.Year2013JournalGeobiologyVolume11Number4Pages377-395DOI10.1111/gbi.12042URLhttps://www.scopus.com/inward/recor.....bedced7e79c3e5ad736a36edbKeywordsbacterial DNAicephospholipidribosome DNARNA 16S, abundancebiogeochemistrycarbon cycledeep-sea benthosheterotrophymarine sedimentmicrobial communitysediment chemistrysediment coresedimentation rate, Antarcticaarchaeonarticlebacterial loadbacteriumbiotacell countchemistryclassificationDNA sequencegeneticsisolation and purificationmicrobiologysediment, Antarctic RegionsArchaeaBacteriaBacterial LoadBiotaCell CountDNA, BacterialDNA, RibosomalGeologic SedimentsIcePhospholipidsRNA, Ribosomal, 16SSequence Analysis, DNA, AntarcticaRoss Ice ShelfWest Antarctica, ActinobacteriaBacteria (microorganisms)BacteroidetesChloroflexiChloroflexi (class)Gammaproteobacteria, rank3

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TypeArticleCitationCarr, S., Vogel, S., Dunbar, R., Brandes, J., Spear, J., Levy, R., Naish, T., Powell, R., Wakeham, S. and Mandernack, K. (2013). Bacterial abundance and composition in marine sediments beneath the {Ross Ice Shelf, Antarctica}. Geobiology, 11(4): 377-395 IdentifierCarr2013Relevancerank3

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Naish, T.