VAAM-Jahrestagung 2011 Karlsruhe, 3.–6. April 2011

EMV005Anaerobic oxidation of methane in Lake ConstancesedimentsJ. Deutzmann*, B. SchinkDepartment of Biologiy, University Konstanz, Konstanz, GermanyFreshwater lakes contribute with 2-10% to the total emissions of the potentgreenhouse gas methane. In Lake Constance aerobic oxidation of methanehas been described extensively, but anaerobic oxidation of methane (AOM)remained cryptic. AOM with sulfate as electron acceptor has been reportedfor various environments including freshwater habitats. Recently also nitrateand nitrite were shown to act as electron acceptors for methane oxidation ineutrophic freshwater systems, and bacteria belonging to the NC10 phylumare capable to carry out this process.We performed tracer experiments to follow 14 CO 2 formation from 14 CH 4anoxically in sediment incubations in the presence of different electronacceptors, namely nitrate, nitrite, and sulfate. The diversity of NC10 phylumbacteria was assessed via clone libraries, and RFLP patterns were used tocompare the community composition between different sediments.No evidence for sulfate-dependent methane oxidation was found, butaddition of nitrate significantly increased 14 CO 2 formation in incubations ofprofundal sediment. In addition, pmoA and 16S rRNA genes and of theNC10 phylum were detected in Lake Constance sediments and revealed thatthe community structure differed between profundal and littoral sediments.These results clearly indicate that Lake Constance sediments have thepotential for anaerobic methane oxidation coupled to denitrification. Thisprocess seems to be more important in profundal sediments than in thelittoral zone, and the differences in the community structure of the NC10bacteria may reflect this disparity. Anaerobic oxidation of methane in-situ ispossibly often masked by aerobic methane oxidation in oligotrophic habitatsdue to the close spatial proximity of the reactant transition zones but maystill play a significant role in mitigating methane emissions.EMV006Half a millimeter makes a difference: a microscale studyon distribution and specific activity of methanotrophs atan oxic-anoxic interfaceA. Reim*, P. Frenzel 1Department of Biogeochemistry, Max Planck Institute for TerrestrialMicrobiology, Marburg, GermanyRice paddies are one of the main global sources of methane, a major greenhouse gas. Considering the importance of rice as a staple crop for a growinghuman population, source strength may even increase further. With themethane emission from rice paddies being drastically reduced by the activityof methanotrophic bacteria, understanding these microorganisms is essential.While diversity and activity of these bacteria on rice roots is intensivelystudied, the soil surface layer with its overlapping methane-oxygen countergradientsis neglected so far.To build a physical model of the surface of a flooded soil, we usedmicrocosms supplementing a thin membrane supported layer of watersaturatedpaddy soil with methane from below and with air from above. Forsampling, the soil was shock-frozen with liquid nitrogen and slicedhorizontally to 0.1 mm thick layers. Community structure was analyzed byT-RFLP, a diagnostic microarray, and by competitive RT-PCR targeting thepmoA gene, a functional and phylogenetic marker for methanotrophs. pmoAtranscripts served as a proxy for species-specific activity.The active community consisted of type I methanotrophs: Methylobacter,Methylococcus and Methylomonas, and representatives of some rice-specificenvironmental clusters. This subcommunity was responsible for methaneoxidation, while type II methanotrophs were abundant, but not detectable atthe mRNA level.It has already been known that the surface layer of flooded soils acts as abiofilter preventing up to 90% of the methane formed in the anoxic bulk soilto escape into the atmosphere. Here we show at the submillimeter scale, howthe very oxic-anoxic interface selects for certain type I methanotrophs thatare the main players, while type II were omnipresent but rarely active.EMV007Archaea dominate the ammonia-oxidizing microbialcommunity in an acidic fenM. Herrmann*, K. Burow, A. Hädrich, K. KüselInstitute of Ecology - Limnology/Aquatic Geomicrobiology, Friedrich-Schiller-University, Jena, GermanyNitrification in fens and bogs is often hampered by low pH, high content ofhumic acids, and lack of oxygen in the water-logged peat soils. So far, onlylittle is known about microbial communities involved in nitrification in theseenvironments. The goals of this study were (i) to assess the potential fornitrification in an acidic fen and (ii) to investigate the communitycomposition, abundance, and transcriptional activity of the microbial groupsinvolved in ammonia oxidation, the first and rate-limiting step ofnitrification, in the peat soil. Samples were obtained from the acidic fenSchlöppnerbrunnen (Fichtelgebirge/Bavaria). Pore water chemical profilesand measurements of potential nitrification activity provided evidence thatthe fen soil harbors active nitrifiers. Communities of ammonia-oxidizingarchaea (AOA) and bacteria (AOB) were analyzed targeting the amoA geneas molecular marker, which encodes ammonia monooxygenase, the keyenzyme of ammonia oxidation. AOA constituted about 1 % of the totalmicrobial community in the upper ten cm of the peat profile andoutnumbered AOB by up to three orders of magnitude. Quantification ofamoA gene transcripts suggested a higher transcriptional activity of AOAunder field conditions as well as in laboratory incubations of peat samples.The diversity of AOA and AOB was low with only a few differentphylotypes. Ongoing experiments aim to estimate the contribution of AOAand AOB to overall nitrification activity in the fen soil.EMV008How does land use influence bacterivorous protists insoils?K. Glaser*, J. Johnke, H. Harms, A. ChatzinotasHelmholtz Center for Environmental Research (UFZ), Leipzig, GermanyThe goal of our project is to correlate molecular diversity patterns of activeand abundant single-cell eukaryotic predators of soil bacteria, the protists,with a land use gradient of agriculturally used grasslands. Bacterivorous soilflagellates represent an integral component of the terrestrial microbial loop.For instance, nutrients immobilized in the microbial biomass can betransferred to higher trophic levels such as plants and thus enhance thenutrient cycle significantly. A well studied example is the increase ofnitrogen uptake in plants due to protist activity. In the framework of theDFG-funded „Biodiversity Exploratories” we hypothesize that the diversityof the protistan „seed bank” (total diversity including inactive dormant cells)and that of the established active population („realized” diversity) will differin response to biotic and abiotic factors. Therefore we choose a cultivationindependentmolecular biological fingerprinting tool, i.e. the T-RFLPmethod that allows us to gain a rapid and reliable overview of the active (i.e.on the RNA-level) and the overall (i.e. on the DNA-level) protist communitycomposition. We studied different phylogenetic levels and taxa (alleukaryotes, the Chrysophyceae and the Kinetoplastea) at four time points in2009 and correlated the obtained patterns with environmental factors likesoil properties, plant diversity and land use regimes. By comparing thepatterns of the realized and total community we could show a strongrelevance of dormancy for soil protists. Furthermore, using quantitative PCRthe underlying abundances of protistan species were estimated. Land useintensity seems to influences not only the protistan abundance but also theproportion of dormant cells in soil. We could partly uncover the response ofthe protists in grasslands to land use regimes and the relevance of dormancyfor the diversity and activity of protists.EMV009Dynamics and drivers of ammonia oxidizing microbes insoilM. SchloterEcogenetics, Helmholz Center Munich, Oberhschleissheim, GermanyIn the last 20 years the use of molecular methods has revolutionizedmicrobial ecology. Today we know that only a small part of the soilmicroflora can be cultivated using classical isolation procedures andfunctional diversity of soils is the best playground on earth, when enzymeswith new properties are in focus. Mainly the role of archaea which has beenspektrum | Tagungsband 2011