VAAM-Jahrestagung 2012 18.–21. März in Tübingen

213Therefore, we hypothesize that both anoxic oxidation and reductivedechlorination may be parallelly occurring pathways for the removal ofMCB and DCBin situ. This study aimed to investigate the microbialtransformation of MCB and DCB in the complex environment of aconstructed planted (Juncus effusus) model scale wetland. Additionallydifferent redox conditions were compared in a laboratory microcosmstudy. After more than 365 days of continuous operation, the overallremoval of MCB was >90% while DCB was completely removed in themodel scale wetland. Concurrent sulphate and iron reduction wasobserved. The original groundwater pumped into the wetland was anoxicand contained ferrous iron and high concentrations of sulphate. Along theflow path, the geochemistry changed. We observed increasing sulphideand iron(II) concentrations in the anoxic and deeper sediment part whereasthe upper zone became oxic and less sulfidic. In the microcosms, MCBmineralisation was observed under nitrate and iron reducing conditions.Microbial community analysis showed the presence of a diversecommunity which could be linked to methanogenic, sulphate or ironreducing (Geobacter) activity as well as to potential aerobic processes(Burkholderia). We identified representatives of the phylum Chloroflexirelated to Dehalogenimonas which could be involved in thedehalogenation of chlorinated contaminants.1. Nijenhuis, I., et al.,Sensitive detection of anaerobic monochlorobenzene degradation using stableisotope tracers.Environmental Science & Technology, 2007.41(11): p. 3836-3842.2. Fung, J.M., et al.,Reductive dehalogenation of dichlorobenzenes and monochlorobenzene tobenzene in microcosms.Environ Sci Technol, 2009.43(7): p. 2302-7.SMV012On the distinct physiological capabilities of so far unculturedarchaea in acidophilic biofilmsS. Ziegler* 1,2 , K. Dolch 1 , J. Majzlan 3 , J. Gescher 11 KIT Karlsruhe, Department for Applied Biology, Karlsruhe, Germany2 Albert Ludwigs University Freiburg, Department for Microbiology, Freiburg,Germany3 Friedrich-Schiller University, Depertment for Mineralogy, Jena, GermanyBiofilms can provide a number of different ecological niches formicroorganisms. The here studied snotite biofilms in which pyriteoxidizing microbes are the primary producers are outstanding objects tostudy multispecies biofilms. This is due to their stability that allows in situmeasurements as well as detailed fluorescence in situ hybridization (FISH)based characterization of the microbial population in different areas of thebiofilm. Consequently, catalyzed reporter deposition (CARD) FISH wasused to examine niches of archaea and bacteria in an acidic snotite biofilm.These results were combined with oxygen microsensor measurements tocorrelate the abundance of different phylogenetic groups to the availableoxygen concentration. This concentration declined rapidly from the outsideto the inside of the biofilm. Hence, part of the population lives undermicrooxic or anoxic conditions. Leptospirillum ferrooxidans strainsdominate the microbial population but are only located in the oxicperiphery of the snotite structure. Acidithiobacillus species were alsodetected but occurred in the oxic periphery as well as the anoxic core.Interestingly, archaea were identified only in anoxic areas of the biofilm.The archaeal community consists of so far uncultured Thermoplasmatalesas well as novel ARMAN species. In addition to CARD FISH and oxygenmicrosensor measurements, in situ microautoradiographic (MAR) FISHwas used to identify areas in which acitive CO 2 fixation took place.Leptospirilla as well as acidithiobacilli were identified as the primaryproducers. CO 2 fixation was revealed to proceed in the outer rim of thematrix. Hence, archaea inhabiting the snotite core do not seem tocontribute to primary production. This work gives insight in the ecologicalniches of acidophilic microorganisms and their role in a consortium. Thedata suggests so far unprecedented capabilities of ARMAN species andcan provide the basis for the isolation of so far uncultured archaea.SMV013Effects of sulfadiazine entering via manure into soil onabundance and transferability of antibiotic resistance in therhizosphere of grass and maizeS. Jechalke* 1 , C. Kopmann 1 , I. Rosendahl 2 , J. Grooneweg 3 ,E. Krögerrecklenfort 1 , U. Zimmerling 1 , V. Weichelt 1 , G.-C. Ding 1 ,J. Siemens 2 , W. Amelung 2 , H. Heuer 1 , K. Smalla 11 Julius Kühn-Institute - Federal Research Centre for Cultivated Plants(JKI), Epidemiology and Pathogen Diagnostics, Braunschweig, Germany2 Institute of Crop Science and Resource Conservation, University of Bonn,Soil Science and Soil Ecology, Bonn, Germany3 Institute of Bio- and Geosciences 3, Agrosphere, ForschungszentrumJülich GmbH, Jülich, GermanyVeterinary antibiotics introduced into soil via manure are assumed topromote the spreading of antibiotic resistance genes and selection ofresistant bacterial populations. The rhizosphere is a hot spot of microbialinteractions like horizontal gene transfer, as root exudates are a foodsource for microorganisms and a driving force of population density andactivity. For example, it was shown that the addition of artificial rootexudates increased the bacterial community tolerance towards theveterinary antibiotic compound sulfadiazine (SDZ) [1]. On the other hand,the exposure of bacteria to SDZ is presumably reduced in the rhizospheresince the dissipation of bioaccessible SDZ-concentrations was recentlyshown to be accelerated in rhizosphere soil, indicating an enhanceddegradation of the compound [2]. However, so far little is known about theabundance and dynamics of sulfonamide resistance genes in therhizosphere. We therefore compared the fate and effect of SDZ in bulkandrhizosphere soil in mesocosms planted with maize and in field plotsplanted with maize or grass. In both experiments, manure was appliedwhich was collected from pigs treated with SDZ or not. SDZconcentrations over time were analyzed by a sequential extraction protocolfor soil yielding antibiotic fractions of different binding strength, whichserved as a proxy for the bioaccessible concentration. Following theapplication of manure, CaCl 2-extractable concentrations of SDZ and itsmetabolites tended to decrease faster in rhizosphere soil than in bulk soilwhereas the dissipation rates of residual microwave-extractable SDZ weresimilar. Quantitative real-time PCR of total community DNA showed thatthe application of manure containing SDZ increased the relative abundanceof the SDZ resistance genes sul1 and sul2 in bulk- and rhizosphere soil ofmaize, which may be associated with a propagation of LowGC-typeplasmids. In the rhizosphere of the field experiment, the difference ofrelativesul abundance between the treatments increased over time, even atbioaccessible SDZ-concentrations below previously reported effectivedoses.1. Brandt, K. K.; Sjoholm, O. R.; Krogh, K. A.; Halling-Sorensen, B.; Nybroe, O., IncreasedPollution-Induced Bacterial Community Tolerance to Sulfadiazine in Soil Hotspots Amended withArtificial Root Exudates. Environmental Science & Technology 2009, 43, (8), 2963-2968.2. Rosendahl, I.; Siemens, J.; Groeneweg, J.; Linzbach, E.; Laabs, V.; Herrmann, C.; Vereecken,H.; Amelung, W., Dissipation and Sequestration of the Veterinary Antibiotic Sulfadiazine and ItsMetabolites under Field Conditions. Environmental Science & Technology 2011, 45, (12), 5216-5222.SMV014The 'rare biosphere' contributes to wetland sulfate reduction -fameless actors in carbon cycling and climate changeM. Pester*, B. Hausmann, N. Bittner, P. Deevong, M. Wagner, A. LoyUniversity of Vienna, Department of Microbial Ecology, Vienna, AustriaWetlands are a major source of the greenhouse gas methane and theirresponse to global warming and increasing aerial sulfur pollution is one ofthe largest unknowns in the upcoming decades to centuries. Althoughregarded as primarily methanogenic environments, biogeochemical studieshave revealed a hidden sulfur cycle in wetlands that can sustain rapidrenewal of the small standing pools of sulfate. Here, we show by 16SrRNA gene stable isotope probing that a Desulfosporosinus species, whichconstitutes only 0.006% of the total microbial community, is a majorsulfate reducer in a long-term experimental peatland field site whensupplied with in situ concentrations of short-chained fatty acids andlactate. Parallel stable isotope probing using dsrAB [encoding subunit Aand B of the dissimilatory (bi)sulfite reductase] identified no additionalsulfate reducers under the conditions tested despite the high diversity ofthis functional marker gene in the studied peatland. Subsequent singlesubstrate incubations revealed that sulfate reduction was stimulated bestwith lactate, propionate, and butyrate but not with acetate or formate. Forthe identified Desulfosporosinus species, a high cell-specific sulfate2-reduction rate of 341 fmol SO 4 cell -1 day -1 was determined. Thus, thesmall Desulfosporosinus population has the potential to reduce sulfate insitu at a rate of up to 36.8 nmol (g soil w. wt.) -1 day -1 , sufficient to accountfor a substantial part of sulfate reduction in the peat soil. Modeling ofsulfate diffusion to such highly active cells identified no limitation insulfate supply even at bulk concentrations as low as 10 M. These datashow that the identified Desulfosporosinus species, despite being amember of the 'rare biosphere', can contribute substantially to sulfatereduction, which diverts the carbon flow in peatlands from methane to CO 2and, thus, alters their contribution to global warming.SMV015Microbial iron cycling in freshwater sedimentsC. Schmidt*, E.-D. Melton, A. KapplerUniversity Tuebingen, Geomicrobiology, Tuebingen, GermanyIron belongs to the dominant chemical elements in the Earth’s crust and istherefore an important constituent in all environmental systems. Iron redoxtransformations and elemental cycling are strongly controlled by localgeochemical conditions, as well as by the abundance and activity of ironoxidizingand iron-reducing microorganisms. Applying a coupledgeochemical-microbiological approach we attempted to determine thespatial distribution of the different iron transformation processes as afunction of substrate, energy and electron donor/acceptor availability infreshwater sediments. As the microbial distribution is a function of localgeochemical conditions we have determined the distribution of readilyavailable electron acceptors (O 2, NO 3 - ) and donors (Fe II ), as well as theabundance of iron-converting microorganisms with high spatial resolution.In addition, the bioavailable fractions of ferriferrous minerals wereBIOspektrum | Tagungsband 2012