Isotopic composition of fatty acids of extremely piezophilic bacteria from the Mariana Trench at 11,000 m |
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| Institution: | 1. Department of Geological and Atmospheric Sciences, Iowa State University, Ames, IA 50011, USA;2. Department of Chemistry, Western Michigan University, Kalamazoo, MI 49008, USA;3. Department of Earth and Environmental Sciences, Rensselaer Polytechnic Institute, Troy, NY 12180, USA;4. The DEEPSTAR group, Japan Marine Science and Technology Center, 2-15 Natsushima-cho, Yokosuka 237, Japan;1. Key Laboratory of Shale Gas and Geoengineering, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, PR China;2. University of Chinese Academy of Sciences, Beijing 100049, PR China;3. Beijing Municipal Environmental Monitoring Center, Beijing 100048, PR China;1. Department of Geophysics, Graduate School of Science, Tohoku University, Sendai, Miyagi 980-8578, Japan;2. Istituto di Astrofisica e Planetologia Spaziali (IAPS), Istituto Nazionale di Astrofisica (INAF), Via del Fosso del Cavaliere 100, 00133 Roma, Italy;1. Center of Deep Sea Research, Institute of Oceanology, Chinese Academy of Sciences, Qingdao 266071, China;2. Laboratory for Marine Ecology and Environmental Science, Qingdao National Laboratory for Marine Science and Technology, Qingdao 266237, China;3. Key Laboratory of Marine Ecosystem and Biogeochemistry, State Oceanic Administration, Second Institute of Oceanography, Ministry of Natural Resources, Hangzhou 310012, China;4. Center for Ocean Mega-Science, Chinese Academy of Sciences, Qingdao 266071, China;5. Key Laboratory of Marine Environment and Ecology, Ministry of Education, Qingdao 266100, China;6. College of Environmental Science and Engineering, Ocean University of China, Qingdao 266100, China;7. Marine Ecology Center, First Institute of Oceanography, Ministry of Natural Resources, Qingdao 266237, China;1. Max Planck Institute for Marine Microbiology, Celsiusstr.1, D-28359, Bremen, Germany;2. Alfred-Wegener-Institute Helmholtz Center for Polar and Marine Research, Am Handelshafen 12, D-27570, Bremerhaven, Germany;3. Japan Agency for Marine-Earth Science and Technology, Division of Biodiversity, Yokosuka, Kanagawa 237-0061, Japan;4. University of Copenhagen, Marine Biological Section, 3000 Helsingør, Denmark;5. Scottish Association for Marine Science, Oban PA37 1QA, UK;6. University of Southern Denmark, Nordic Centre for Earth Evolution, Odense M-5230, Denmark;7. University of Aarhus, Arctic Research Centre, Aarhus, Denmark |
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| Abstract: | Two extremely piezophilic bacteria, DB21MT-2 and DB21MT-5, isolated from sediments of the Mariana Trench at 11,000 m, were grown in the laboratory under low-temperature (10 °C) and high-pressure (70 MPa) conditions. Phospholipid ester-linked fatty acids (PLFA) were analyzed by gas chromatography/mass spectrometry (GC/MS) and isotopic compositions of individual fatty acids were determined by gas chromatography isotope ratio mass spectrometry (GC-IRMS) in order to determine isotopic fractionation effects during biosynthesis. The piezophiles are characterized by fatty acids with carbon chains ranging from 14 to 22 carbons in length and by the presence of abundant polyunsaturated fatty acids (PUFA). Fatty acids from each culture exhibit a wide range of isotopic compositions (δ13C vs. Pee Dee Belemnite (PDB)). With two exceptions (C15:0 and C17:1 from DB21MT-2), all fatty acids are depleted in 13C relative to that of bulk carbon in the bacterial growth substrate. In addition, strain DB21MT-2 shows systematically higher (less negative) δ13C values than strain DB21MT-5. The implications for isotope fractionation in fatty acid biosynthesis and the interpretation of isotopic composition of sedimentary fatty acids are discussed. It is suggested that the same type of microorganisms could have rather different δ13C under the same growth conditions, and that sedimentary fatty acids with distinct δ13C values do not necessarily have to originate from different organisms. Interpretation of δ13C values of sedimentary biomarkers may be complicated by such large variations in δ13C of fatty acids given that they are biosynthesized by the same type of microorganisms grown under identical conditions. |
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