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  • 1
    Publication Date: 2010-02-13
    Description: The Ediacaran Period (635 to 542 million years ago) was a time of fundamental environmental and evolutionary change, culminating in the first appearance of macroscopic animals. Here, we present a detailed spatial and temporal record of Ediacaran ocean chemistry for the Doushantuo Formation in the Nanhua Basin, South China. We find evidence for a metastable zone of euxinic (anoxic and sulfidic) waters impinging on the continental shelf and sandwiched within ferruginous [Fe(II)-enriched] deep waters. A stratified ocean with coeval oxic, sulfidic, and ferruginous zones, favored by overall low oceanic sulfate concentrations, was maintained dynamically throughout the Ediacaran Period. Our model reconciles seemingly conflicting geochemical redox conditions proposed previously for Ediacaran deep oceans and helps to explain the patchy temporal record of early metazoan fossils.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Li, Chao -- Love, Gordon D -- Lyons, Timothy W -- Fike, David A -- Sessions, Alex L -- Chu, Xuelei -- New York, N.Y. -- Science. 2010 Apr 2;328(5974):80-3. doi: 10.1126/science.1182369. Epub 2010 Feb 11.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Earth Sciences, University of California, Riverside, CA 92521, USA. chaoli@ucr.edu〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/20150442" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; *Biological Evolution ; Carbonates/analysis ; China ; Ferrous Compounds/analysis ; *Fossils ; Geologic Sediments/*chemistry ; Hydrogen Sulfide ; Iron ; Oceans and Seas ; Oxidation-Reduction ; Oxygen/*analysis ; Seawater/*chemistry ; Sulfates/analysis
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 2
    Publication Date: 2014-11-08
    Description: In the low-oxygen Archean world (〉2400 million years ago), seawater sulfate concentrations were much lower than today, yet open questions frustrate the translation of modern measurements of sulfur isotope fractionations into estimates of Archean seawater sulfate concentrations. In the water column of Lake Matano, Indonesia, a low-sulfate analog for the Archean ocean, we find large (〉20 per mil) sulfur isotope fractionations between sulfate and sulfide, but the underlying sediment sulfides preserve a muted range of delta(34)S values. Using models informed by sulfur cycling in Lake Matano, we infer Archean seawater sulfate concentrations of less than 2.5 micromolar. At these low concentrations, marine sulfate residence times were likely 10(3) to 10(4) years, and sulfate scarcity would have shaped early global biogeochemical cycles, possibly restricting biological productivity in Archean oceans.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Crowe, Sean A -- Paris, Guillaume -- Katsev, Sergei -- Jones, CarriAyne -- Kim, Sang-Tae -- Zerkle, Aubrey L -- Nomosatryo, Sulung -- Fowle, David A -- Adkins, Jess F -- Sessions, Alex L -- Farquhar, James -- Canfield, Donald E -- New York, N.Y. -- Science. 2014 Nov 7;346(6210):735-9. doi: 10.1126/science.1258966.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Microbiology and Immunology and Department of Earth, Ocean, and Atmospheric Sciences, University of British Columbia, Vancouver, British Columbia, Canada. NordCEE and Department of Biology, University of Southern Denmark, Odense, Denmark. sacrowe1@gmail.com. ; Department of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA 91125, USA. ; Large Lakes Observatory and Department of Physics, University of Minnesota, Minneapolis, MN 55812, USA. ; Department of Microbiology and Immunology and Department of Earth, Ocean, and Atmospheric Sciences, University of British Columbia, Vancouver, British Columbia, Canada. NordCEE and Department of Biology, University of Southern Denmark, Odense, Denmark. ; School of Geography and Earth Sciences, McMaster University, Hamilton, Ontario, Canada. ; Department of Earth and Environmental Sciences, University of St. Andrews, St. Andrews, UK. ; Research Center for Limnology, Indonesian Institute of Sciences, Cibinong, West Java, Indonesia. ; Department of Geology, University of Kansas, Lawrence, KS 66045, USA. ; Department of Geology, University of Maryland, College Park, MD 20742, USA. ; NordCEE and Department of Biology, University of Southern Denmark, Odense, Denmark.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/25378621" target="_blank"〉PubMed〈/a〉
    Keywords: Biological Products/chemical synthesis/chemistry/*history ; History, Ancient ; Indonesia ; Seawater/*chemistry ; Sulfates/analysis/*history ; Sulfur Isotopes/analysis/history
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 3
    Publication Date: 2005-10-01
    Description: Laterally extensive black shales were deposited on the Sao Francisco craton in southeastern Brazil during low-latitude Neoproterozoic glaciation approximately 740 to 700 million years ago. These rocks contain up to 3.0 weight % organic carbon, which we interpret as representing the preserved record of abundant marine primary productivity from glacial times. Extractable biomarkers reflect a complex and productive microbial ecosystem, including both phototrophic bacteria and eukaryotes, living in a stratified ocean with thin or absent sea ice, oxic surface waters, and euxinic conditions within the photic zone. Such an environment provides important constraints for parts of the "Snowball Earth" hypothesis.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Olcott, Alison N -- Sessions, Alex L -- Corsetti, Frank A -- Kaufman, Alan J -- de Oliviera, Tolentino Flavio -- New York, N.Y. -- Science. 2005 Oct 21;310(5747):471-4. Epub 2005 Sep 29.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Earth Sciences, University of Southern California, Los Angeles, CA 90089, USA. olcott@usc.edu〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/16195425" target="_blank"〉PubMed〈/a〉
    Keywords: Bacterial Physiological Phenomena ; Biomarkers/analysis ; Brazil ; Carbon/*analysis ; Carbon Isotopes/analysis ; Carbonates/analysis ; Cyanobacteria/physiology ; *Ecosystem ; Geologic Sediments/*chemistry ; *Ice Cover ; Organic Chemicals/*analysis ; *Photosynthesis ; Seawater/*microbiology ; Sunlight
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 4
    Publication Date: 2014-06-28
    Description: Methane is an important greenhouse gas and energy resource generated dominantly by methanogens at low temperatures and through the breakdown of organic molecules at high temperatures. However, methane-formation temperatures in nature are often poorly constrained. We measured formation temperatures of thermogenic and biogenic methane using a "clumped isotope" technique. Thermogenic gases yield formation temperatures between 157 degrees and 221 degrees C, within the nominal gas window, and biogenic gases yield formation temperatures consistent with their comparatively lower-temperature formational environments (〈50 degrees C). In systems where gases have migrated and other proxies for gas-generation temperature yield ambiguous results, methane clumped-isotope temperatures distinguish among and allow for independent tests of possible gas-formation models.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Stolper, D A -- Lawson, M -- Davis, C L -- Ferreira, A A -- Santos Neto, E V -- Ellis, G S -- Lewan, M D -- Martini, A M -- Tang, Y -- Schoell, M -- Sessions, A L -- Eiler, J M -- New York, N.Y. -- Science. 2014 Jun 27;344(6191):1500-3. doi: 10.1126/science.1254509.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Division of Geological and Planetary Sciences, California Institute of Technology, 1200 East California Boulevard, Pasadena, CA 91125, USA. dstolper@caltech.edu. ; ExxonMobil Upstream Research Company, Houston, TX, USA. ; Division of Geochemistry, Petrobras Research and Development Center (CENPES), Rio de Janeiro, RJ, Brazil. ; U.S. Geological Survey, Denver Federal Center, Denver, CO, USA. ; Department of Geology, Amherst College, Amherst, MA, USA. ; Power, Environmental, and Energy Research Institute, Covina, CA, USA. ; GasConsult International Inc, Berkeley, CA, USA. ; Division of Geological and Planetary Sciences, California Institute of Technology, 1200 East California Boulevard, Pasadena, CA 91125, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/24970083" target="_blank"〉PubMed〈/a〉
    Keywords: Biodegradation, Environmental ; Carbon Isotopes ; Euryarchaeota/*metabolism ; Gases ; Hot Temperature ; Methane/*biosynthesis/*chemistry ; Models, Theoretical ; *Oil and Gas Fields/microbiology ; Petroleum/metabolism ; Temperature
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 5
    Publication Date: 2014-11-08
    Description: Mass-independent fractionation of sulfur isotopes (reported as Delta(33)S) recorded in Archean sedimentary rocks helps to constrain the composition of Earth's early atmosphere and the timing of the rise of oxygen ~2.4 billion years ago. Although current hypotheses predict uniformly negative Delta(33)S for Archean seawater sulfate, this remains untested through the vast majority of Archean time. We applied x-ray absorption spectroscopy to investigate the low sulfate content of particularly well-preserved Neoarchean carbonates and mass spectrometry to measure their Delta(33)S signatures. We report unexpected, large, widespread positive Delta(33)S values from stratigraphic sections capturing over 70 million years and diverse depositional environments. Combined with the pyrite record, these results show that sulfate does not carry the expected negative Delta(33)S from sulfur mass-independent fractionation in the Neoarchean atmosphere.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Paris, G -- Adkins, J F -- Sessions, A L -- Webb, S M -- Fischer, W W -- P41GM103393/GM/NIGMS NIH HHS/ -- New York, N.Y. -- Science. 2014 Nov 7;346(6210):739-41. doi: 10.1126/science.1258211.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA 91125, USA. gparis@caltech.edu. ; Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA 91125, USA. ; Stanford Synchrotron Radiation Lightsource, Menlo Park, CA 94025, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/25378622" target="_blank"〉PubMed〈/a〉
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 6
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  • 8
    Publication Date: 2009-07-17
    Print ISSN: 0027-8424
    Electronic ISSN: 1091-6490
    Topics: Biology , Medicine , Natural Sciences in General
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  • 9
    Publication Date: 2007-09-11
    Print ISSN: 0027-8424
    Electronic ISSN: 1091-6490
    Topics: Biology , Medicine , Natural Sciences in General
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  • 10
    Publication Date: 2011-11-09
    Description: Rhodopseudomonas palustris TIE-1 is a Gram-negative bacterium that produces structurally diverse hopanoid lipids that are similar to eukaryotic steroids. Its genome encodes several homologues to proteins involved in eukaryotic steroid trafficking. In this study, we explored the possibility that two of these proteins are involved in intracellular hopanoid transport. R. palustris has a sophisticated membrane system comprising outer, cytoplasmic, and inner cytoplasmic membranes. It also divides asymmetrically, producing a mother and swarmer cell. We deleted genes encoding two putative hopanoid transporters that belong to the resistance–nodulation–cell division superfamily. Phenotypic analyses revealed that one of these putative transporters (HpnN) is essential for the movement of hopanoids from the cytoplasmic to the outer membrane, whereas the other (Rpal_4267) plays a minor role. C30 hopanoids, such as diploptene, are evenly distributed between mother and swarmer cells, whereas hpnN is required for the C35 hopanoid, bacteriohopanetetrol, to remain localized to the mother cell type. Mutant cells lacking HpnN grow like the WT at 30 °C but slower at 38 °C. Following cell division at 38 °C, the ΔhpnN cells remain connected by their cell wall, forming long filaments. This phenotype may be attributed to hopanoid mislocalization because a double mutant deficient in both hopanoid biosynthesis and transport does not form filaments. However, the lack of hopanoids severely compromises cell growth at higher temperatures more generally. Because hopanoid mutants only manifest a strong phenotype under certain conditions, R. palustris is an attractive model organism in which to study their transport and function.
    Print ISSN: 0027-8424
    Electronic ISSN: 1091-6490
    Topics: Biology , Medicine , Natural Sciences in General
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