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

212SMV008Methanol Consumption by Methylotrophs in TemperateAerated SoilsA. Stacheter*, H.L. Drake, S. KolbUniversity of Bayreuth, Department of Ecological Microbiology, Bayreuth,GermanyMethanol is the second most abundant organic molecule in the atmosphere.The main source of atmospheric methanol is plant material. Methanoloxidation by aerobic microorganisms in soils might be an important sink inthe global methanol cycle. Aerobic methylotrophs use methanol as asource of carbon and energy. Methanol oxidation kinetics were previouslyunknown. Currently, only few studies addressed structures of methanolutilisingmicrobial communities in aerated soils. Apparent Michaelis-Menten-Kinetics were experimentally determined in soil slurries that weresupplemented with 14 C-methanol. 14 CO 2 production was measured, andrecovery of 14 C was calculated. Soil slurries with supplemental cyanideserved as controls for abiotic activity, and were not substantially activecompared to cyanide-free and methanol-supplemented slurries. Thus,methanol oxidation was primarily a biotic process. Washed roots from agrassland soil, and sterile grown Arabidopsis sp. plants exhibited lowermethanol oxidation rates than root-free soil. Thus, not plant tissue butlikely soil microorganisms were the main drivers of methanol oxidation.The K M(app) in a grassland soil (National Park Hainich) was 0.2 mmol perL. It is in the range of K M-values of purified methanol dehydrogenases ofthe soil-borne methylotroph Hyphomicrobium denitrificans (0.2-168 mmolper L), which implies that likely methanol oxidation of the grassland soilwas catalysed by methylotrophs. The in situ methylotroph communitycomposition will be analysed in soil samples from the National ParkHainich by pyrosequencing of functional genes (mxaF, fae, mch) that aremandatory for methanol metabolism of methylotrophs. An analysis ofmxaF genotype composition over the incubation period of the 14 C-methanol-experiment will provide information on responding keymethylotrophs.SMV017Effects of elevated CO 2 concentrations on microbial ecosystemat the artificial test site ASGARD, EnglandS. Gwosdz* 1 , J. West 2 , D. Jones 2 , K. Smith 3 , M. Krüger 11 Bundesanstalt für Geowissenschaften und Rohstoffe, Geochemie undRohstoffe, Hannover, Germany2 British Geological Survey, Nottingham, United Kingdom3 University of Nottingham, Nottingham, United KingdomIncreasing anthropogenic CO 2 emissions will lead to climate change andocean acidification with severe consequences for ecosystems(Intergovernmental Panel on Climate Change, 2007). CO 2 capture andstorage into geological formations like deep saline aquifers or depleted gasand oil reservoirs is one option to reduce greenhouse gas emissions.As part of the EU funded “RISCS” project (Research into Impacts andSafety in CO 2 storage), a study investigating the impacts of potential CO 2leakages on near-surface environments is being undertaken. To assesseffects of potential CO 2 release at CO 2-non-adapted sites, microbialabundance, diversity and plant coverage at the ASGARD site (Artificial SoilGassing and Response Detection, Nottingham) before, during and after CO 2exposure are being studied.Examination of environmentally important metabolic pathways and microbialgroups showed clear differences between CO 2 injected plots with high (100%),medium (70%) and low (10%) CO 2 concentrations and control plots.Increasing rates of methanogenesis and methane oxidation at high CO 2concentrations were provided. CO 2 production rates as an importantindicator for microbial activity showed decreasing trends under elevatedCO 2 concentrations. Analysis of the microbial community composition byquantitative real time PCR and investigations of the microbial diversity(e.g. sequencing, TRFLP) illustrate alterations in microbial abundancesunder CO 2 influence.Our results indicate a shift towards anaerobic and acid tolerant microbialpopulations.SMV009Evidence of aerobic polycyclic aromatic hydrocarbon (PAH)biodegradation in a contaminated aquifer by combiningBACTRAP ® s and laboratory microcosms.A. Bahr* 1 , P. Bombach 1,2 , A. Fischer 21 Helmholtz Centre for Environmental Research - UFZ, Department ofIsotope Biogeochemistry, Leipzig, Germany2 Isodetect GmbH, Leipzig, GermanyPolycyclic aromatic hydrocarbons (PAH) are among the most abundantgroundwater contaminants, mostly as a result of petroleum and diesel spillsand industrial processes. Due to their toxic, carcinogenic and mutageniccharacteristics, cost-effective clean up strategies such as MonitoredNatural Attenuation (MNA) are required for their removal fromcontaminated field sites. PAHs have been shown to be biodegradabledespite the high activation energy needed to attack the aromatic ring andtheir tendency to sorb on hydrophobic surfaces thus hampering thebiodegradation. Evidence for active PAH biodegradation in situ is difficultto obtain and requires suitable approaches for the routine application in theevaluation of NA potentials.In this study, biodegradation of four polycyclic aromatic hydrocarbons(naphthalene, acenaphthene, fluorene, and phenanthrene) wasdemonstrated at a PAH-contaminated aquifer. In situ microcosms(BACTRAP ® s) consisting of activated carbon pellets were loaded with[ 13 C 6]-naphthalene or [ 13 C 5/ 13 C 6]-fluorene (50:50) and incubated for over 2months in monitoring wells to collect indigenous groundwatercommunities. Amino acids extracted from the developed microbialcommunities showed 13 C-incorporation of up to 30.4 atom%, thusdemonstrating a highly active PAH-degrading microbial community at thefield site. To further assess the biodegradation potential for the PAHs,laboratory microcosms were set up with [ 13 C 6]-naphthalene, [ 13 C 5/ 13 C 6]-fluorene (50:50), [ 13 C 1]-acenaphthene or [ 13 C 1]-phenanthrene. In situmicrocosms exposed over a period of 99 days in field monitoring wellsand groundwater samples served as inoculum for the laboratorymicrocosms. Analysis of 13 C-incorporation into the produced CO 2 usinggas chromatography coupled to isotope ratio mass spectrometry (GC-IRMS) revealed a high degradation potential for all tested PAHs. Thecombined application of BACTRAP ® s and laboratory microcosms can be apowerful tool for evaluating PAH biodegradation at subsurface impactedsites. The BACTRAP ® system turned out to be suitable to study thedegradation activity directly at the field site, but also facilitated enrichmentof PAH-degrading communities for further laboratory cultivationexperiments.SMV010Cobalt trace metal requirement for reductive dechlorinationof trichloroethene by DehalococcoidesM.B. Loganathan, A. Kappler, S. Behrens*Center for Applied Geosciences, Geosciences, Tübingen, GermanyThe genus Dehalococcoides plays a key role in the completedechlorination of chlorinated ethenes because these bacteria are the onlymicroorganisms known that are capable of reductive dechlorinationbeyond dichloroethene (DCE) to vinyl chloride (VC) and ethene. Thereduction of chloroethenes by Dehalococcoides spp. is catalyzed byreductive dehalogenase (RDase) enzymes. The RDases inDehalococcoides spp. are monomeric, vitamin B 12-dependent enzymes. Acomparative genome analyses of trace element utilization in prokaryotesand eukaryotes revealed that Dehalococcoides have the largest cobaltrequiringmetalloproteome among all sequenced prokaryotic genomeswhich is consistent with the high number of non-identical RDasehomologs per genome (up to 36 in strain VS). Here we describe reductivedechlorination of trichloroethene (TCE) by a microbial mixed culturecontaining Dehalococcoides spp. in a defined mineral medium amendedwith varying concentrations of cobalt (0.6 M to 2064 M). We observedthat elevated cobalt concentrations have a positive effect on cell growthand the rate of dechlorination by Dehalococcoides spp.. However,complete dechlorination of TCE to ethene and the highest cell yields wereonly obtained in enrichment cultures containing 36 M cobalt. Enrichmentcultures with significantly higher or lower cobalt concentrations showedmainly incomplete dechlorination leading to the accumulation of cis-DCEand VC. qPCR analysis showed that defined cobalt concentrations can leadto the selective enrichment of Dehalococcoides spp.. We also observedthat Dehalococcoides containing different sets of chloroethene reductivedehalogenases react differently to cobalt. While 36 M cobalt lead to theenrichment of VC and TCE reductive dehalogenase (vcrA/tceA)-containingDehalococcoides other cobalt concentrations favoured only TCE reductivedehalogenase (tceA)-containing Dehalococcoides strains. Our experimentsdemonstrate how careful evaluation of findings from comparativegenomics can further our understanding of the physiological requirementsof environmental microorganisms with implications for their application inbioremediation.SMV011Anaerobic transformation of chlorobenzene and dichlorobenzenein highly contaminated groundwaterM. Schmidt*, I. Nijenhuis, D. Wolfram, S. Devakota, J. Birkigt, B. Klein,H.H. RichnowHelmholtz Centre for Environmental Research - UFZ , IsotopeBiogeochemistry, Leipzig, GermanyThe halogenated groundwater pollutants chlorobenzene (MCB) anddichlorobenzene (DCB) are ubiquitous in the environment and seem to bepersistent and accumulating under anoxic aquifer conditions. However, ourgroup could provide evidence for the transformation of chlorobenzeneunder anoxic conditions [1]. Futhermore Fung et al. [2]described thedehalogenation of DCB and MCB in anoxic microcosms.BIOspektrum | Tagungsband 2012