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

EMV017Calcite biomineralization in a karstic cave - bacteriahidden in the darkA. Rusznyak* 1 , D.M. Akob 1 , S. Nietzsche 2 , T.R. Neu 3 , K. Küsel 11 Institute of Ecology, AG Aquatic Geomicrobiology, Friedrich-Schiller-University, Jena, Germany2 Center of Electron Microscopy, Friedrich-Schiller-University, Jena,Germany3 Helmholtz Center for Environmental Research (UFZ), Magdeburg,GermanyKarstic caves represent one of the most important subterranean carbonstorages on Earth and provide excellent „windows” to the subsurface. Ourmultidisciplinary study took advantage of the recent discovery of theHerrenberg Cave to investigate its mineralogy and the diversity and potentialrole of bacteria in carbonate mineral formation. Stalactites consisted ofcalcite, while dolomite and calcite (besides quartz, muscovite and clayminerals) were found in sediments, suggesting that only calcite wasprecipitating from seepage water as stalactites. Confocal laser scanningmicroscopy detected bacterial cells on the surface and in the interior ofstalactites. Molecular analyses revealed the dominance of Proteobacteriainhabiting stalactites and fluvial sediments in addition to the phylaBacteroidetes, Acidobacteria, Nitrospira, Chloroflexi, Planctomycetes,Verrucomicrobia, Actinobacteria and Firmicutes. Up to 16 % of thesequences were related to yet unclassified Bacteria. A large fraction of thesebacteria were metabolically active. Arthrobacter sulfonivorans andRhodococcus globerulus strains isolated from the cave formed mixtures ofcalcite, vaterite and monohydrocalcite. R. globerulus precipitatedidiomorphous, rhombohedral carbonate crystals, while with A. sulfonivoransxenomorphous globular crystals were observed. The different crystalmorphologies refer to species dependent calcite formation and underline theimportance for biomineralization in karstic habitats.EMV018Abundance of microbes involved in nitrogentransformation in the rhizosphere of Leucanthemopsisalpina (L.) Heywood grown in soils from different sites ofthe Damma glacier forefieldS. Töwe* 1 , A. Albert 2 , K. Kleineidam 3 , R. Brankatschk 4 , J.C. Munch 1 ,J. Zeyer 4 , M. Schloter 31 Department of Soil Ecology, Technical University Munich, Neuherberg,Germany2 Department of Environmental Engineering, Helmholtz Center Munich,Neuherberg, Germany3 Department of Terrestrial Ecogenetics, Helmholtz Center Munich,Neuherberg, Germany4 Institute of Biogeochemistry and Pollutant Dynamics, Swiss FederalInstitute of Technology, Zurich, SwitzerlandGlacier forefields are an ideal playground to investigate the role ofdevelopment stages of soils on the formation of plant-microbe interactions,as within the last decades many alpine glaciers retreated, whereby releasingand exposing parent material for soil development. Especially the status ofmacronutrients like nitrogen differs between soils of different developmentstages in these environments and may influence plant growth significantly.Thus in this study, we reconstructed major parts of the nitrogen cycle in therhizosphere soil/root system of Leucanthemopsis alpina (L.) Heywood aswell as the corresponding bulk soil by quantifying functional genes ofnitrogen fixation (nifH), nitrogen mineralization (chiA, aprA), nitrification(amoA AOB, amoA AOA) and denitrification (nirS, nirK, and nosZ) in a 10-year and a 120-year ice-free soil of the Damma glacier forefield. We linkedthe results to the ammonium and nitrate concentrations of the soils as well asto the nitrogen and carbon status of the plants. The experiment wasperformed in a greenhouse simulating the climatic conditions of the glacierforefield. Samples were taken after 7 and 13 weeks of plant growth. HighestnifH gene abundance in connection with lowest nitrogen content of L. alpinawas observed in the 10-year soil after 7 weeks of plant growth,demonstrating the important role of associative nitrogen fixation for plantdevelopment in this soil. In contrast, in the 120-year soil copy numbers ofgenes involved in denitrification, mainly nosZ, were increased after 13weeks of plant growth, indicating an overall increased microbial activitystatus as well as higher concentrations of nitrate in this soil.EMV019Ultrastructural, genomic and ecological analysis of„Candidatus Magnetobacrterium bavaricum” reveals amechanism homologous to proteobacterial magnetosomeformationC. Jogler* 1 , G. Wanner 2 , S. Kolinko 2 , M. Niebler 2 , W. Lin 3 , Y. Pan 3 ,P. Stief 4 , A. Beck 4 , D. de Beer 4 , R. Amann 4 , N. Petersen 2 , M. Kube 5 ,R. Reinhardt 5 , D. Schüler 21 Department of Microbiology and Molecular Genetics, Harvard MedicalSchool, Boston, USA2 Ludwig-Maximilians-University, Munich, Germany3 Institute of Geology and Geophysics, Chinese Academy of Sciences,Beijing, China4 Max Planck Institute for Marine Microbiology, Bremen, Germany5 Max Planck Institute for Molecular Genetics, Berlin, GermanyMagnetotactic bacteria (MTB) are phylogenetically diverse. They useintracellular membrane-enclosed magnetite crystals called magnetosomesfor navigation in their aquatic habitats, which are of broad interdisciplinaryinterest. Due to the lack of cultivated representatives from other phyla, thegenetic background of magnetosome formation was exclusively analyzed ina few closely related members of the Proteobacteria thus far, in which allessential functions required for magnetosome formation are encoded withina large genomic magnetosome island. However, the evolutionary origin andphylogenetic distribution of this magnetosome island has been unknown,and it has been questioned whether homologous genes are present in MTBfrom other phyla.Here, we present the analysis of the uncultivated „CandidatusMagnetobacterium bavaricum” (Mbav) from the Nitrospira-phylum bycombining ecological and geochemical techniques with metagenomics,single cell sorting and a variety of advanced electron microscopic methods.Micromanipulation and whole genome amplification of individual sortedcells revealed Mbav-specific sequences that were used for screening ofmetagenomic libraries. This led to the identification of a genomic clustercontaining several magnetosome genes with homology to those inProteobacteria. Different electron microscopic imaging techniques, such asfocused ion beam milling or ultrathin sectioning of high-pressure frozen andfreeze-substituted cells revealed a complex cell envelope and an intricatemagnetosome architecture. In particular, the presence of magnetosomemembranes as well as cytoskeletal magnetosome filaments suggests asimilar mechanism of magnetosome formation in Mbav as inProteobacteria. Altogether, our findings suggest a monophyletic origin ofmagnetotaxis, and relevant genes were likely transferred horizontallybetween Proteobacteria and representatives of the Nitrospira-phylum.EMV020Comparison of Genotypic, Proteotypic and PhenotypicMethods for the Identification of BacteriaM. Patel, S. Polson, U. Herbert*Accugenix, Marketing, Newark, USAAccurate classification of unknown bacterial isolates is an essential first stepin understanding the impact these organisms have on an environmentalmonitoring program. There are many methods, technologies, and strategiesutilized to determine the identity of unknown microorganisms, however, theselection of these methods is often impacted by more than the performanceof the technology. Cost, time and the amount of expertise required toperform an assay are major points to consider during the selection process.Current available methods of identification range from genotypic tophenotypic, with 16S sequencing being universally acknowledged as thestandard for routine bacterial identifications. Still, there is even variabilitywithin this process as not all 16S sequencing methods are comparable.When identifications are based on phenotypic characteristics, the methodsare more subjective and results can be impacted by many variables. The firstpractical proteotypic identification systems utilize matrix-assisted laserdesorption/ionization - time of flight (MALDI-TOF) spectroscopy formicrobial identification. This technology is based on whole cell proteinprofiles that are subject to less expression variability than phenotypicsystems. This study directly compared performance between several of thesetechnologies, including metabolic profiling (bioMerieux VITEK® 2Compact), MALDI-TOF (Bruker BioTyper), automated DNA sequenceanalysis (ABI MicroSEQ® 2.1), and DNA sequencing with a referencequality,customized data analysis process and curated libraries (Accugenix).These microbial identification methods were used to analyze 60 unknownenvironmental bacterial isolates. Accuracy, as well as assay cost, time, andspektrum | Tagungsband 2011