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

most abundant members of natural populations, which were assigned toProteobacteria and the Nitrospira phyla. Here, we used a novel approachthat allowed the targeted phylogenetic and ultrastructural analysis ofindividual, low abundant MTB cells from environmental samples.Morphologically conspicous single cells were micromanipulated frommagnetically collected multi-species MTB populations, which was followedby whole genome amplification (WGA) and electron microscopic analysisof sorted cells. Phlyogenetic identity of target cells was verified byfluorescence in situ hybridization (FISH) with probes derived from 16SrDNA sequences that were PCR-amplified from WGAs. Application of thisapproach to various freshwater and marine sediment samples revealedextensive and novel diversity of MTB, which escaped detection by parallelconventional 16S rRNA gene clone library analysis. While most of thenewly identified MTB belonged to various lineages of Proteobacteria andthe Nitrospira phylum, one morphotype termed SKK-01 could be assignedto the candidate division OP3, which extends the phylogenetic diversity ofMTB to a new phylum. FISH demonstrated that SKK-01 represents only amarginal fraction of the MTB population (~ 10 -5 ). Besides intracellularsulfur inclusions, SKK-01 harbors ~175 bullet-shaped magnetosomesarranged in multiple chains which consist of magnetite as revealed by TEMand EDX analysis.In conclusion, our approach represents a powerful tool for targeted singleanalysisof low-abundance uncultivated prokaryotes from environmentalsamples.MDV002Complexity of the bacterial community in the sediment ofthe drinking water reservoir Saidenbach obtained bypyrosequencingK. Röske* 1 , I. Röske 21 Institute for Microbiology, Sächsische Akademie der Wissenschaften zuLeipzig, University of Technology, Dresden, Germany2 Institute for Microbiology, University of Technology, Dresden, GermanyThe Sediment is an important compartment of freshwater ecosystems withfavorable living conditions for a large number of bacterial species alongchanging redox conditions. Although microbes play an important role for theflux of matter and being part of the major biogeochemical cycles very littleis known about their diversity in freshwater sediments. Here we present astudy of the microbial diversity in sediment samples taken at three differentlocations and two sediment depths in the mesotrophic drinking waterreservoir Saidenbach in Germany. The selected sampling sites comprisedifferent environmental conditions. A pyrosequencing approach was used toanalyse parts of the V6 and V7 region of the bacterial 16S rRNA gene.17,751 sequences were classified into 21 phyla. The largest phylum with50.7% of all sequences was Proteobacteria with a range of 37 to 64% in theindividual samples. The rarefaction curves calculated at sequencedivergence of 3% showed no saturation indicating that the full extent ofgenetic diversity was not covered. For all samples the Shannon index ofdiversity (H’) was high and ranged from 7.29 to 7.53. Among the bacteria,the dominant groups were the Betaproteobacteria, DeltaproteobacteriaBacteroidetes, Verrucomicrobia, Acidobacteria, Gammaproteobacteria,Alphaproteobacteria Firmicutes, Chloroflexi, Nitrospira and Actinobacteria,representing 27.9%, 11.9%, 11.6%, 7,2%, 4.6%, 3.3%, 2.4%, 1.8%, 1.3%,1% and 0.7% respectively, of all classified sequences. Differences in thecommunity composition were observed between the sampling sites as wellas with sediment depth. While one sampling site contained a largeabundance of Fusobacteria in the upper 0.5cm sediment layer they werescarce in deeper sediment layers and at the other sampling sites.Surprisingly, the genus Nitrospira was found especially in the lowerinvestigated sediment horizon (3-5cm sediment depth) where oxygen andnitrate were depleted and an increasing ammonium concentration wasobserved. The majority of Deltaproteobacteria could be classified into 3families: Syntrophaceae, Geobacteraceae with the genus Geobacter andDesulfobacteriaceae.The pyrosequencing approach in combination with the environmentalconditions provided new information on this complex ecosystem.MDV003A close look at the diversity and dynamics of ultraoligotrophicgroundwater microbial communities duringthe restoration of a drinking water wellC. Karwautz*, K. Hörmann, T. LuedersHelmholtz Center, Neuherberg, GermanyMicrobial monitoring of drinking water production and distribution systemsis essential to assure water quality and to predict possible risks. Chemicaland biological characteristics of the water pumped are checked regularly;however microbiological data is still based on outdated culturing tests. Here,we characterise intrinsic groundwater microbial communities before, duringand after the mechanical restoration of a drinking water production well.High pressure jetting and hydrofracturing are procedures routinely usedperiodically to impede well clogging by fine sediments and also biofilms.Microbial communities sampled from the groundwater were first screenedby T-RFLP fingerprinting of intrinsic Bacteria, Archaea andMicroeukaryontes. This revealed similar communities in water before andafter well cleaning, however OTU abundances were more even afterwards.In contrast, well jetting preferentially purged only a subset of the dominatingOTUs, indicating a tendency for attached growth in the well. Moreover,massively paralleled 454-pyrotag sequencing was performed. We usedbidirectional sequencing of bacterial rRNA gene amplicons (~520 bp) whichallowed for assembly, T-RF prediction and phylogenetic placement ofdominating amplicon contigs. This data is still under analysis, but willillustrate a unique time series of drinking water microbial community detailsbefore and after well rehabilitation. Novel insights into microbialcommunities in groundwater wells will be provided, which improves ourknowledge on the ecology of this ultra-oligotrophic habitat and also possiblepools and fluxes of microbial taxa and potential pathogens.MDV004Recovery of methanotrophs from disturbance:population dynamics, evenness, and functioning.A. Ho*, C. Lüke, P. FrenzelDepartment of Biogeochemistry, Max Planck Institute for TerrestrialMicrobiology, Marburg, GermanyBiodiversity is claimed being essential for ecosystem functioning, butthreatened by anthropogenic disturbances. Prokaryotes have been assumedto be functionally redundant and virtually inextinguishable. However, recentwork indicates that microbes may well be sensitive to environmentaldisturbance. Focusing on methane oxidizing bacteria as model organisms,we simulated disturbance-induced mortality by mixing native with sterilizedpaddy soil in two ratios, 1:4 and 1:40, representing moderate and severe dieoffs.Disturbed microcosms were compared to an untreated control.Recovery of activity and populations was followed over four months bymethane uptake measurements, pmoA-qPCR, pmoA-based T-RFLP (terminalrestriction fragment length polymorphism), and a pmoA-based diagnosticmicroarray. Diversity and evenness of methanotrophs decreased in disturbedmicrocosms, but functioning was not compromised. We consistentlyobserved distinctive temporal shifts between type I and type IImethanotrophs, and a rapid population growth leading to even higher cellnumbers comparing disturbed microcosms to the control. Overcompensatingmortality suggested that population size in the control was limited bycompetition with other bacteria. Overall, methanotrophs showed aremarkable ability to compensate for die-offs.MDV005Life in the cold, dark south - Microbial communities ofmarine methane seeps at Hikurangi margin (NewZealand)S.E. Ruff* 1 , J. Arnds 2 , K. Knittel 2 , R. Amann 2 , G. Wegener 1 , A. Ramette 1 ,A. Boetius 11 Microbial Habitat Group, Max Planck Institute for Marine Microbiology,Bremen, Germany2 Department of Molecular Ecology,Max Planck Institute for MarineMicrobiology, Bremen, GermanyMarine methane seeps and associated chemosynthetic communities havebeen studied extensively in recent years. Many exciting discoveries havebeen made concerning the biodiversity of microbial communities, theirspektrum | Tagungsband 2011