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

209cyclotron resonance mass spectrometry (FTICR-MS) provided firstinsights into the metabolic pathways active in P. amoebophila EBs andshowed that: (I) P. amoebophila EBs take up D-glucose and several aminoacids in host free environments and incorporate carbon and nitrogen intotheir biomass. (II) Host free-incubated P. amoebophila EBs release 13CO2from 13C-D-glucose, which is a clear indication for respiration. (III) Bioconversionof glucose was observed and suggested synthesis of sugarpolymers, which likely serve as storage compounds. (IV) The availabilityof D-glucose during host-free incubation significantly affects maintenanceof infectivity. In summary, our data clearly demonstrate metabolic activityof P. amoebophila EBs. Intriguingly, this active metabolism seems to playa key role for maintenance of infectivity and establishment of a symbioticrelationship with its amoeba host.SIV6-FGBacteria-zooplankton interactions: a key to understandingbacterial dynamics and biogeochemical processes in lakes?H.-P. Grossart* 1,2 , C. Dziallas 1 , K.T. Tang 1,31 Leibniz Institute of Freshwater Ecology and Inland Fisheries, Stechlin, UnitedStates2 University of Potsdam, Institute for Biochemistry and Biology , Potsdam,Germany3 College of William & Mary, Virginia Institute of Marine Science, Gloucester,United StatesWorldwide, metazoan zooplankton represents an enormous surface andbiomass in pelagic systems but their linkage with bacteria has beenassumed to be rather indirect (via nutrient cycling and trophic cascades).However, a zooplankter’s body carries a high abundance of diversebacteria, which can account for a substantial fraction and diversity ofpelagic bacteria. Zooplankton bodies are organic-rich micro-environmentsthat support fast bacterial growth. Their physical-chemical conditionsdiffer from those in the surrounding water and hence select for differentbacterial communities. Until now, information on bacteria-zooplanktoninteractions is still limited to only a few zooplankton groups andenvironments, in particular copepods in coastal and estuarine waters.Therefore, our proposal focuses on bacteria-zooplankton interactions inlakes. Since zooplankton taxa can have very different life history traits wewill compare a large number of zooplankton taxa in a variety of lakes. Infield and lab studies we will investigate these interactions with a highspatial and temporal resolution. We will address 4 topics: A) spatial andtemporal variations in bacteria-zooplankton association, B) microbialdynamics in the zooplankton gut microhabitat, C) bacterial dispersal bymigrating zooplankton and D) effects on microbial activities during themid-summer zooplankton decline. We aim to fundamentally change theway we understand pelagic food webs and the ecological role of bacteriametazoaninteractions.SIV7-FGEfflux pumps and TetR-like regulators in rhizobialinteractions with plantsB. Kranzusch 1 , S. Albert 1 , K. Kunze 1 , M. Kunke 1 , A. Weiss 1 ,E. Szentgyörgyi 1 , O. Walser 2 , M. Göttfert 1 , S. Rossbach* 11 Technische Universität Dresden, Institut für Genetik, Dresden, Germany2 Western Michigan University, Department of Biological Sciences,Kalamazoo, United StatesOur goal is to analyze the importance of efflux pumps that are being usedby plant-associated bacteria to defend themselves against secondary plantmetabolites. In Bradyrhizobium japonicum and in Sinorhizobium meliloti,the nitrogen-fixing symbionts of soybean and alfalfa, respectively, genesencoding efflux pumps of the major facilitator superfamily have beenfound to be induced by plant flavonoids. Interestingly, adjacent to thesegenes are genes encoding TetR-like regulators. The respective intergenicregions contain several palindromic structures, presumably binding sitesfor the TetR-like proteins. Our comparative analysis, concomitantlycarried out with B. japonicum and S. meliloti, characterizes the binding ofpurified regulator proteins to the operator regions, determines the influenceof flavonoids on the binding affinities, analyzes the expression of theefflux pump genes in dependence of flavonoids, and determines thephenotype of bacterial mutants concerning their resistance towards plantderivedcompounds and their competitiveness in plant-bacteriainteractions. These studies will shed further light on the intricacies of themolecular signal exchange between rhizobia and their legume host plants.SIV8-FGHost colonization of bifidobacteria - from genome sequence toprotein functionD. Zhurina, M. Gleisner, C. Westermann, J. Schützner, C.U. Riedel*University of Ulm, Institute of Microbiology and Biotechnology, Ulm,GermanyBifidobacteria are one of the major bacterial groups of the human colonicmicroflora and are widely used as probiotics due to their reported healthpromotingeffects. Bifidobacterium bifidum S17, B. longum ssp. infantisE18 and B. breve S27 were shown to have opposing phenotypes regardingadhesion to intestinal epithelial cells (IECs) and anti-inflammatory effects.While B. bifidum S17 tightly adheres to cultured IECs and showsprominent anti-inflammatory effects both in vitro and in several murinemodels of colitis, the other two strains show week adhesion and no antiinflammatorycapacity [1, 2].In order to study these differences in more detail, we sequenced thegenomes of these strains [3, unpublished data] and analysed them with aspecial focus on factors involved in adhesion and host colonization. Alarge number of proteins were identified in all strains that display domainspotentially involved in adhesion to host tissues. All strains possess geneclusters, which show high similarity to genes encoding for pili structures inGram-positive bacteria, and the corresponding genes are differentiallyexpressed in the tested bifidobacteria under in vitro conditions.Comparison to other genome sequences led to the identification of alipoprotein of the bacterial cell envelope, which is specific for the speciesB. bifidum. Functional analysis revealed that this protein plays animportant role in adhesion of B. bifidum strains to IECs. Furthermore, agene encoding a subtilisin-family protease was identified in the genome ofB. bifidum S17, which might be involved in host colonization and/orprobiotic effects. The corresponding gene was cloned and expressed in E.coli and purified protein was analysed for its substrate specificity.Using genome sequencing, comparative analysis and functionalcharacterisation, a number of factors were identified in different strains ofbifidobacteria, which could play an important role in host colonization ofthese important human symbiotic bacteria.1. J. Preising, D. Philippe, M. Gleinser, H. Wei, S. Blum, B.J. Eikmanns, J.H. Niess, C.U. Riedel. Appliedand Environmental Microbiology 76 (2010): 3048-51.2. D. Philippe, E. Heupel, S. Blum-Sperisen, C.U. Riedel. International Journal of Food Microbiology 149(2011): 45-9.3. D. Zhurina, A. Zomer, M. Gleinser, V.F. Brancaccio, M. Auchter, M.S. Waidmann, C. Westermann, D.van Sinderen, C.U. Riedel. Journal of Bacteriology 193 (2011): 301-2.SIP1-FGHost species-specific Thiothrix ectosymbionts on cave-dwellingamphipodsJ. Bauermeister* 1 , D. Ionescu 2 , A. Ramette 3 , T. Vagner 4 ,M.M.M. Kuypers 4 , S. Dattagupta 11 Georg-August University Göttingen, Courant Research CenterGeobiology, Göttingen, Germany2 Max Planck Institute for Marine Microbiology, Microsensor Group,Bremen, Germany3 Max Planck Institute for Marine Microbiology, HGF-MPG Group forDeep Sea Ecology and Technology, Bremen, Germany4 Max Planck Institute for Marine Microbiology, Department ofBiogeochemistry, Bremen, GermanySymbioses between invertebrates and chemoautotrophic microbes arecommon in the marine environment, and ecologically dominant at deepseahydrothermal vents, cold seeps, and coastal sediments. The associationbetween Niphargus ictus amphipods and Thiothrix bacteria, found in theFrasassi caves of central Italy, is the first known example of achemoautotrophic symbiosis from a freshwater habitat. The Frasassi cavesystem is forming by sulfuric acid-driven limestone dissolution and hostsan underground ecosystem sustained by chemoautotrophy. Thick mats offilamentous sulfur-oxidizing gamma- and epsilonproteobacteria cover thesulfidic cave water bodies. Gammaridean amphipods of the genusNiphargus interact directly with these bacterial mats, but only a specificThiothrix phylotype, which is rarely found in the mats, has been identifiedon their exoskeletons [1].When the symbiosis was first described, it was assumed to involve onlyone host species, N. ictus. Subsequent molecular and morphologicalanalyses revealed that there are two other Niphargus species in Frasassi,and that the three species have independently invaded the cave ecosystem[2]. Scanning Electron Microscopy (SEM) showed that these twoadditional species also harbor filamentous bacteria, and their assignment tothe sulfur-oxidizing Thiothrix clade was confirmed based on their 16SrRNA gene sequences. Phylogenetic analyses and Fluorescence In SituHybridization (FISH) revealed that the three Niphargus species harborthree different Thiothrix symbionts, one of which is specific to one host,and two of which are shared between two hosts. Automated RibosomalIntergenic Spacer Analyses (ARISA) showed that the distribution of theseThiothrix symbionts among Niphargusis strongly host species-specific.The three Niphargusspecies display different locomotive behaviors and occupydistinct microhabitats within the cave system. Consequently, they might exposeBIOspektrum | Tagungsband 2012