title: Microbial Response to Experimentally Controlled Redox Transitions at the Sediment Water Interface.
abstract: The sediment-water interface of freshwater lakes is characterized by sharp chemical gradients, shaped by the interplay between physical, chemical and microbial processes. As dissolved oxygen is depleted in the uppermost sediment, the availability of alternative electron acceptors, e.g. nitrate and sulfate, becomes the limiting factor. We performed a time series experiment in a mesocosm to simulate the transition from aerobic to anaerobic conditions at the sediment-water interface. Our goal was to identify changes in the microbial activity due to redox transitions induced by successive depletion of available electron acceptors. Monitoring critical hydrochemical parameters in the overlying water in conjunction with a new sampling strategy for sediment bacteria enabled us to correlate redox changes in the water to shifts in the active microbial community and the expression of functional genes representing specific redox-dependent microbial processes. Our results show that during several transitions from oxic-heterotrophic condition to sulfate-reducing condition, nitrate-availability and the on-set of sulfate reduction strongly affected the corresponding functional gene expression. There was evidence of anaerobic methane oxidation with NOx. DGGE analysis revealed redox-related changes in microbial activity and expression of functional genes involved in sulfate and nitrite reduction, whereas methanogenesis and methanotrophy showed only minor changes during redox transitions. The combination of high-frequency chemical measurements and molecular methods provide new insights into the temporal dynamics of the interplay between microbial activity and specific redox transitions at the sediment-water interface.
authors.affiliation: Department of Soil Science, Institute for Crop Science and Resource Conservation (INRES), University of Bonn, Nußallee 13, Bonn, Germany.
authors.forename: Katharina
authors.initials: K
authors.lastname: Frindte
authors.affiliation: Berlin Center for Genomics in Biodiversity Research (BeGenDiv), Königin-Luise-Straße 6-8, Berlin, Germany.
authors.forename: Martin
authors.initials: M
authors.lastname: Allgaier
authors.affiliation: Leibniz-Institute of Freshwater Ecology and Inland Fisheries, Alte Fischerhütte 2, Stechlin, Germany.|Institute of Biochemistry and Biology, University of Potsdam, Am Neuen Palais 10, Potsdam, Germany.
authors.forename: Hans-Peter
authors.initials: HP
authors.lastname: Grossart
authors.affiliation: Israel Oceanographic and Limnological Research, The Yigal Allon Kinneret Limnological Laboratory, Migdal, Israel.
authors.forename: Werner
authors.initials: W
authors.lastname: Eckert
mesh_terms: D000693:Anaerobiosis; D001419:Bacteria / Q000378:metabolism; D001673:Biodegradation, Environmental; D016000:Cluster Analysis; D018076:DNA, Complementary / Q000737:chemistry; D058645:Denaturing Gradient Gel Electrophoresis; D004784:Environmental Monitoring / Q000379:methods*; D005618:Fresh Water / Q000737:chemistry* / Q000382:microbiology; D019015:Geologic Sediments / Q000737:chemistry* / Q000382:microbiology; D005858:Germany; D008697:Methane / Q000737:chemistry; D059013:Microbial Consortia; D009566:Nitrates / Q000737:chemistry; D009569:Nitric Oxide / Q000737:chemistry; D010084:Oxidation-Reduction; D010100:Oxygen / Q000737:chemistry; D010802:Phylogeny; D016133:Polymerase Chain Reaction; D012313:RNA / Q000737:chemistry; D012336:RNA, Ribosomal, 16S / Q000032:analysis; D013440:Sulfides / Q000737:chemistry; D014871:Water Microbiology
chemical_list: D018076:DNA, Complementary; D009566:Nitrates; D012336:RNA, Ribosomal, 16S; D013440:Sulfides; D009569:Nitric Oxide; D012313:RNA; D008697:Methane; D010100:Oxygen