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      Modified Lipid Extraction Methods for Deep Subsurface Shale


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          Growing interest in the utilization of black shales for hydrocarbon development and environmental applications has spurred investigations of microbial functional diversity in the deep subsurface shale ecosystem. Lipid biomarker analyses including phospholipid fatty acids (PLFAs) and diglyceride fatty acids (DGFAs) represent sensitive tools for estimating biomass and characterizing the diversity of microbial communities. However, complex shale matrix properties create immense challenges for microbial lipid extraction procedures. Here, we test three different lipid extraction methods: modified Bligh and Dyer (mBD), Folch (FOL), and microwave assisted extraction (MAE), to examine their ability in the recovery and reproducibility of lipid biomarkers in deeply buried shales. The lipid biomarkers were analyzed as fatty acid methyl esters (FAMEs) with the GC-MS, and the average PL-FAME yield ranged from 67 to 400 pmol/g, while the average DG-FAME yield ranged from 600 to 3,000 pmol/g. The biomarker yields in the intact phospholipid Bligh and Dyer treatment (mBD + Phos + POPC), the Folch, the Bligh and Dyer citrate buffer (mBD-Cit), and the MAE treatments were all relatively higher and statistically similar compared to the other extraction treatments for both PLFAs and DGFAs. The biomarker yields were however highly variable within replicates for most extraction treatments, although the mBD + Phos + POPC treatment had relatively better reproducibility in the consistent fatty acid profiles. This variability across treatments which is associated with the highly complex nature of deeply buried shale matrix, further necessitates customized methodological developments for the improvement of lipid biomarker recovery.

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              Distributions of microbial activities in deep subseafloor sediments.

              S D'Hondt (2004)
              Diverse microbial communities and numerous energy-yielding activities occur in deeply buried sediments of the eastern Pacific Ocean. Distributions of metabolic activities often deviate from the standard model. Rates of activities, cell concentrations, and populations of cultured bacteria vary consistently from one subseafloor environment to another. Net rates of major activities principally rely on electron acceptors and electron donors from the photosynthetic surface world. At open-ocean sites, nitrate and oxygen are supplied to the deepest sedimentary communities through the underlying basaltic aquifer. In turn, these sedimentary communities may supply dissolved electron donors and nutrients to the underlying crustal biosphere.

                Author and article information

                Front Microbiol
                Front Microbiol
                Front. Microbiol.
                Frontiers in Microbiology
                Frontiers Media S.A.
                25 July 2017
                : 8
                [1] 1Department of Geology and Geography, West Virginia University Morgantown, WV, United States
                [2] 2Civil, Environmental and Geodetic Engineering, The Ohio State University Columbus, OH, United States
                [3] 3Center for Environmental Biotechnology, University of Tennessee Knoxville, TN, United States
                Author notes

                Edited by: Jennifer F. Biddle, University of Delaware, United States

                Reviewed by: Helen F. Fredricks, Woods Hole Oceanographic Institution, United States; Greg F. Slater, McMaster University, Canada; Sabine Kerstin Lengger, Plymouth University, United Kingdom

                *Correspondence: Rawlings N. Akondi raakondinkerh@ 123456mix.wvu.edu

                This article was submitted to Extreme Microbiology, a section of the journal Frontiers in Microbiology

                Copyright © 2017 Akondi, Trexler, Pfiffner, Mouser and Sharma.

                This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

                Page count
                Figures: 5, Tables: 3, Equations: 0, References: 78, Pages: 15, Words: 11895
                Funded by: National Science Foundation 10.13039/100000001
                Award ID: 1342732
                Award ID: 1342701
                Award ID: 1205596

                Microbiology & Virology

                plfa, dgfa, microbial biomass, deep subsurface, shale ecosystem


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