Woods Hole Oceanographic Institution

Marco Coolen

»Bioavailability of soil organic matter and microbial community dynamics upon permafrost thaw
»7000 years of virus-host molecular dynamics in the Black Sea
»Preservation potential of ancient DNA in Pleistocene marine sediments: Implications for paleoenvironmental reconstructions
»Source-specific variability in post-depositional DNA preservation with potential implications for DNA-based paleecological records
»Exploring preserved ancient dinoflagellalte and haptophyte DNA signatures to infer ecological and environmental conditions during sapropel S1 formation in the eastern Mediterranean
»Ancient DNA in lake sediment records
»Vertical distribution of metabolically active eukaryotes in the water column and sediments of the Black Sea
»DNA and lipid molecular stratigraphic records of haptophyte succession in the Black Sea during the Holocene
»Diversity of Archaea and potential for crenarchaeotal nitrification of group 1.1a in the rivers Rhine and TĂȘt
»Holocene sources of fossil BHPs
»An unusual 17[α],21[β](H)-bacteriohopanetetrol in Holocene sediments from Ace Lake (Antarctica)
»Holocene sources of organic matter in Antarctic fjord
»Variations in spatial and temporal distribution of Archaea in the North Sea
»Archaeal nitrifiers in the Black Sea
»Pleistocene Mediterranean sapropel DNA
»Rapid sulfurisation of highly branched isoprenoid (HBI) alkenes in sulfidic Holocene sediments
»Aerobic and anaerobic methanotrophs in the Black Sea water column
»Fossil DNA in Cretaceous Black Shales: Myth or Reality?
»Sulfur and methane cycling during the Holocene in Ace Lake (Antarctica)
»Ancient algal DNA in the Black Sea
»Archaeal nitrification in the ocean
»Characterization of microbial communities found in the human vagina by analysis of terminal restriction fragment length polymorphisms of 16S rRNA genes
»Biomarker and 16S rDNA evidence for anaerobic oxidation of methane and related carbonate precipitation in deep-sea mud volcanoes of the Sorokin Trough, Black Sea
»Temperature-dependent variation in the distribution of tetraether membrane lipids of marine Crenarchaeota: Implications for TEX86 paleothermometry
»Paleoecology of algae in Ace Lake
»Evolution of the methane cycle in Ace Lake (Antarctica) during the Holocene: Response of methanogens and methanotrophs to environmental change
»Ongoing modification of Mediterranean Pleistocene sapropels mediated by prokaryotes.
»Microbial communities in the chemocline of a hypersaline deep-sea basin (Urania basin, Mediterranean Sea)
»Functional exoenzymes as indicators of metabolically active bacteria in 124,000-year-old sapropel layers of the Eastern Mediterranean Sea
»Specific detection of different phylogenetic groups of chemocline bacteria based on PCR and denaturing gradient gel electrophoresis of 16S rRNA gene fragments
»Analysis of subfossil molecular remains of purple sulfur bacteria in a lake sediment
»Effects of nitrate availability and the presence of Glyceria maxima the composition and activity of the dissimilatory nitrate-reducing bacterial community
»Microbial activities and populations in upper sediment and sapropel layers

Coolen, M. J. L., H. M. Talbot, B. A. Abbas, C. Ward, S. Schouten, J. K. Volkman and J. S. Sinninghe Damsté, Sources for sedimentary bacteriohopanepolyols as revealed by 16S rDNA stratigraphy, Environmental Microbiology, 10(7), 1783-1803, (2008)

Bacteriohopanoids are widespread lipid biomarkers in the geosphere and first appeared in the Archean. Many aerobic and anaerobic bacteria are potential sources of these lipids which can make it difficult to use these biomarkers as accurate proxies for climate-induced ecological and environmental changes. Therefore, we applied preserved 16S ribosomal RNA genes (16S rDNA) to identify Holocene biological sources of BHPs in the sulfidic sediments of the permanently stratified post-glacial Ace Lake, Antarctica. A suite of intact bacteriohopanepolyols (BHPs) were identified by HPLC APCI-MS, which revealed a variety of structural forms whose composition differed through the sediment core reflecting changes in bacterial populations induced by dramatically changing salinity. Stable isotopic compositions of the hopanols formed from periodic acid-cleaved BHPs, showed that some were substantially depleted in 13C, indicative of their methanotrophic origin. Using sensitive molecular tools, we found that both Type I and II methanotrophic bacteria (respectively Methylomonas and Methylocystis) were unique to the oldest lacustrine sediments (>9,400 years BP), but quantification of fossil DNA revealed that the Type I methanotrophs, including methanotrophs related to methanotrophic gill symbionts of deep-sea cold-seep mussels, were the main precursors of the 35-amino BHPs amino-pentol, -tetrol, and -triol. After isolation of the lake ~3000 years ago, one Type I methanotroph of the “methanotrophic gill symbionts cluster” remained the most obvious source of aminotetrol and -triol. The cyanobacterial marker 2-methylbacteriohopanetetrol coincided with the unique presence of a Synechococcus phylotype related to pelagic freshwater strains in the oldest sediments deposited under freshwater conditions. This combined application of advanced geochemical and paleogenomical tools has revealed new insights about the paleoenvironmental evolution of Ace Lake.Full article is available here

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