title: Tracking activity and function of microorganisms by stable isotope probing of membrane lipids.
abstract: Microorganisms in soils and sediments are highly abundant and phylogenetically diverse, but their specific metabolic activity and function in the environment is often not well constrained. To address this critical aspect in environmental biogeochemistry, different methods involving stable isotope probing (SIP) and detection of the isotope label in a variety of molecular compounds have been developed. Here we review recent progress in lipid-SIP, a technique that combines the assimilation of specific13C-labeled metabolic substrates such as inorganic carbon, methane, glucose and amino acids into diagnostic membrane lipid compounds. Using the structural characteristics of certain lipid types in combination with genetic molecular techniques, the SIP approach reveals the activity and function of distinct microbial groups in the environment. More recently, deuterium labeling in the form of deuterated water (D2O) extended the lipid-SIP portfolio. Since lipid biosynthetic pathways involve hydrogen (H+) uptake from water, lipid production can be inferred from the detection of D-assimilation into these compounds. Furthermore, by combining D2O and13C-inorganic carbon (IC) labeling in a dual-SIP approach, rates of auto- and heterotrophic carbon fixation can be estimated. We discuss the design, analytical prerequisites, data processing and interpretation of single and dual-SIP experiments and highlight a case study on anaerobic methanotrophic communities inhabiting hydrothermally heated marine sediments.
authors.affiliation: Max Planck Institute for Marine Microbiology, Celsiusstraße 1, 28359 Bremen, Germany; MARUM Center for Marine Environmental Sciences, Leobener Straße, 28359 Bremen, Germany. Electronic address: gwegener@mpi-bremen.de.
authors.forename: Gunter
authors.initials: G
authors.lastname: Wegener
authors.affiliation: Department of Earth Science and Marine Science Institute, University of California, Santa Barbara, CA 93106, USA.
authors.forename: Matthias Y
authors.initials: MY
authors.lastname: Kellermann
authors.affiliation: MARUM Center for Marine Environmental Sciences, Leobener Straße, 28359 Bremen, Germany.
authors.forename: Marcus
authors.initials: M
authors.lastname: Elvert
mesh_terms: D001419:Bacteria / Q000378:metabolism*; D002247:Carbon Isotopes / Q000032:analysis*; D007553:Isotope Labeling / Q000379:methods*; D008563:Membrane Lipids / Q000032:analysis* / Q000737:chemistry*
chemical_list: D002247:Carbon Isotopes; D008563:Membrane Lipids