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

fluxes via plant into rhizosphere and, subsequently, microbial communitystructure and gene abundance.functional flagellar filament and that glycosylation of these subunits isessential for flagellar assembly and function.EMP016Two extracellular nucleases influence biofilm formationof Shewanella oneidensis MR-1J. Gödeke, M. Heun*, K. Paul, K. ThormannDepartment of Ecophysiology, Max Planck Institute for TerrestrialMicrobiology, Marburg, GermanyMany bacteria species, such as the gram-negative, metal-ion reducingbacterium Shewanella oneidensis MR-1 are known to form densely packedcommunities called biofilms. In this structure, cells are enclosed by a selfproducedmatrix of extracellular polymeric substances (EPS) consisting ofproteins, exopolysacharides, lipids, and extracellular DNA (eDNA). Besideits role during biofilm formation eDNA is widespread among aquaticenvironments and can be exploited by S. oneidensis MR-1 as a source ofcarbon, nitrogen and phosphorus. In this study we investigated the role oftwo extracellular endonucleases, ExeM and ExeS, for biofilm formation andutilization of eDNA. In contrast to ExeS, which was previously found insupernatants, ExeM contains a predicted membrane anchor and has beenidentified in outer-membrane fractions of S. oneidensis MR-1 cultures. Wedemonstrated that deletions of both nucleases do not influence the ability ofutilizing eDNA. Interestingly, biofilm formation is influenced in mutantstrains. Under static conditions, a strain lacking exeS forms a more robustbiofilm, whereas the mutation does not affect biofilms under hydrodynamicconditions. Deletion of exeM results in a strongly decreased biofilm in astatic assay. Under hydrodynamic conditions, ΔexeM forms more denselypacked structures covered by a very thick layer of eDNA compared to S.oneidensis MR-1 wild type. In addition, the expression of both nucleases isdifferentially regulated during biofilm formation and is under control of twomaster regulatory systems, the Arc and the cAMP/CRP system. Theseresults indicate an important role of the two extracellular nucleases duringbiofilm formation by degradation of the important structural matrixcomponent eDNA.EMP017Role of flagellar glycosylation for Shewanella oneidensisMR-1 motility and flagellar assemblyS. Bubendorfer* 1 , K. Dohlich 2 , P. Grassi 3 , A. Dell 3 , K. Thormann 11 Department of Ecophysiology, Max Planck Institute for TerrestrialMicrobiology, Marburg, Germany2 Max Planck Institute for Infection Biology, Berlin, Germany3 South Kensington Campus, Imperial College London, London, UnitedKingdomThe γ-proteobacterium Shewanella oneidensis MR-1 is motile by a singlepolar flagellum. Depending on the environmental sodium-ion concentration,the flagellar motor is driven by Na + - or proton gradients. In the past years ithas been elucidated that flagellins, the major structural components of theflagellar filament, of many bacteria are posttranslationally modified byglycan species via O-linkage. Glycosylation of flagellin appears to be morecommon as previously thought; however its underlying mechanism is quiteversatile among prokaryotes. It has been shown that glycosylation offlagellin subunits plays an important role in virulence of many bacterialpathogenic species and can also be involved in the flagellar assembly.A transposon mutagenesis screening for motility identified a FliA (σ 28 )-dependent gene cluster encoding for proteins which may be important forglycosylating proteins. This prompted us to elucidate the role and functionof glycosylation of two identified flagellins for the assembly of a functionalflagellum and the motility of S. oneidensis MR-1. Mutations in each of thefive genes within the cluster displayed a defect in flagella mediated motilityon swarm plates which was due to aberrant flagellar assembly, which wasalso confirmed by electron microscopy. Alteration in flagellar assembly andmotility was most likely due to posttranslational modification as mutantslacking genes of the putative glycosylation cluster displayed a significantmass shift of the major flagellin subunit. MALDI-TOF and LC coupledtandem MS analyses of purified flagellar filaments clearly identifiedglycosylation at least at 13 potential sites of either serine or threonine withinthe variable region of both flagellin subunits of S. oneidensis MR-1. Theexact sugar composition and the resulting glycan structure remains to bedetermined.Concluding from these results we could demonstrate that S. oneidensis MR-1 possesses two flagellin subunits which are required to assemble aEMP018Will not be presented!EMP019Identification and characterisation of microbialcommunities converting hydrocarbons to methaneF. Gründger* 1 , S. Feisthauer 2 , H.H. Richnow 2 , F. von Netzer 3 , T. Lüders 3 ,M. Krüger 11 Federal Institute for Geosciences and Natural Resources,Geomicrobiology, Hannover, Germany2 Department of Isotope Biogeochemistry, Helmholt Center Munich forEnvironmental Research, Leipzig, Germany3 Institute of Groundwater Ecology, Helmholtz Center Munich, Neuherberg,GermanyAgainst the backround of decreasing conventional resources, especially oil,the search for new energy sources becomes increasingly important. Onecontribution might be the microbial conversion of oil or coal to methane. Inrecent years, the exploration of deep microbial life in the earth´s subsurfacehas become an intriguing and challenging new topic in modern geoscience.Still, only little knowledge has been gained about the metabolic processesand the involved microorganisms in methanogenic hydrocarbonbiodegradation.Consequently, in the DFG-SPP 1319 project we started to investigate thephysiological characteristics of microbial consortia with enrichmentcultures. These microbials are capable to degrade alkanes and aromatichydrocarbons under methanogenic conditions. Our study aims atinvestigating the specific methanogenic community compositionparticipating in the hydrocarbon degradation process. This will lead to abetter understanding of the actively degrading microorganisms, theirmechanistic aspects, formation of metabolites, kinetics and carbon flows.Laboratory microcosms from different habitats (e.g. freshwater ditches,marine sediments, contaminated aquifers) showed high methane productionrates after the addition of oil or coals, and single hydrocarbons. The T-RFLPfingerprints of microbial enrichments showed a large bacterial diversitywhile the archaeal one was limited to three or four dominant species. Thequantification showed high abundances of Archaea and Bacteria in allenrichment cultures. Genes indicative of metal reduction, sulphate reduction,and methanogenesis were also detected in high numbers in theseincubations. In a second stage we performed stable isotope probingexperiments with several 13 C-labelled substrates to reveal the carbon flow infreshwater enrichments. These experiments revealed after molecular andbiochemical analysis the active community taking part in degrading thehydrocarbons.In conclusion our study has shown that an active hydrocarbon degradingcommunity can be enriched from different habitats. These methanogenicconsortia will be further characterised to evaluate enzymatic pathways andthe individual role of the syntrophic partners.EMP020Will not be presented!EMP021Spatial and temporal dynamics in a tar oil contaminatedaquifer and its biochemical consequences tobiodegradationA. Bayer*, G. Pilloni, B. Anneser, T. Lueders, C. GrieblerInstitute of Groundwater Ecology, Helmholtz Center Munich, Neuherberg,GermanyIntroduction of organic contaminants, in a nature state, as aromatichydrocarbons into a porous aquifer leads to the formation of a plume with acharacteristic redox zonation along its horizontal and vertical axes. Theidentification of steep small-scale physical-chemical and microbial gradientsby high-resolution multi-level sampling of groundwater and sedimentallowed the identification and localization of biodegradation processes in atar oil contaminated sandy aquifer in Duesseldorf, Germany. Sulfatespektrum | Tagungsband 2011